My MacBook Pro is walking, not running, slow

Question

My MacBook Pro, circa early 2011 is getting progressively slower. I recently installed Yosemite, but the slow down had already started before that. It is not always consistently slow, at times it is fine. Sometimes however, when I type, the text takes around 30 seconds or more to even show up. Sometimes it never shows up at all. I play a guessing game as to whether or not I need to retype the sentence, usually to find out I didn't, it was just taking a minute this time. Safari may sit for a few minutes before responding, and yes the router is working fine, all our other devices have no problems getting out. I have repaired permissions and I have cleared some hard drive space so I have over 70GB free.
Thanks for your help,
here is the Etre System Report:
Problem description:
MacBook Pro is running painfully slow. but not consistently. At times I will type and it may take 30 seconds or more for the text to show up. Applications may creep or not work at all. I recently upgraded to Yosemite, but the slow down started prior to that. I have repaired permissions and cleared hard drive space as well.
EtreCheck version: 2.0.11 (98)
Report generated November 9, 2014 at 3:41:38 PM EST
Hardware Information: ℹ️
  MacBook Pro (17-inch, Early 2011) (Verified)
  MacBook Pro - model: MacBookPro8,3
  1 2.2 GHz Intel Core i7 CPU: 4-core
  8 GB RAM Upgradeable
  BANK 0/DIMM0
  4 GB DDR3 1333 MHz ok
  BANK 1/DIMM0
  4 GB DDR3 1333 MHz ok
  Bluetooth: Old - Handoff/Airdrop2 not supported
  Wireless:  en1: 802.11 a/b/g/n
Video Information: ℹ️
  Intel HD Graphics 3000 - VRAM: 512 MB
  Color LCD 1920 x 1200
  AMD Radeon HD 6750M - VRAM: 1024 MB
System Software: ℹ️
  OS X 10.10 (14A389) - Uptime: 4:5:20
Disk Information: ℹ️
  TOSHIBA MK7559GSXF disk0 : (750.16 GB)
  S.M.A.R.T. Status: Verified
  EFI (disk0s1) <not mounted> : 210 MB
  Recovery HD (disk0s3) <not mounted>  [Recovery]: 650 MB
  Macintosh HD (disk1) /  [Startup]: 748.93 GB (74.86 GB free)
  Core Storage: disk0s2 749.30 GB Online
  MATSHITADVD-R   UJ-8A8 
USB Information: ℹ️
  Apple Inc. FaceTime HD Camera (Built-in)
  Apple Inc. Apple Internal Keyboard / Trackpad
  Apple Inc. BRCM2070 Hub
  Apple Inc. Bluetooth USB Host Controller
  Logitech USB Receiver
  Apple Computer, Inc. IR Receiver
Thunderbolt Information: ℹ️
  Apple Inc. thunderbolt_bus
Gatekeeper: ℹ️
  Mac App Store and identified developers
Kernel Extensions: ℹ️
  /Applications/Lytro Desktop.app
  [not loaded] com.lytro.Firefly (4.2 - SDK 10.7) Support
  /Library/Sophos Anti-Virus/InterCheck.app
  [not loaded] com.sophos.kext.sav (7.3.0) Support
  /System/Library/Extensions
  [not loaded] com.aliph.driver.jstub (1.1.2 - SDK 10.7) Support
  [not loaded] com.wacom.kext.wacomtablet (6.3.5 - SDK 10.8) Support
Startup Items: ℹ️
  Aladdin: Path: /System/Library/StartupItems/Aladdin
  Startup items are obsolete and will not work in future versions of OS X
Launch Agents: ℹ️
  [not loaded] com.adobe.AAM.Updater-1.0.plist Support
  [running] com.adobe.AdobeCreativeCloud.plist Support
  [running] com.canon.MFManager.plist Support
  [loaded] com.google.keystone.agent.plist Support
  [loaded] com.hp.StatusMonitor.plist Support
  [loaded] com.oracle.java.Java-Updater.plist Support
  [invalid?] com.wacom.SketchManager.plist Support
  [running] com.wacom.wacomtablet.plist Support
Launch Daemons: ℹ️
  [loaded] com.adobe.fpsaud.plist Support
  [running] com.crashplan.engine.plist Support
  [loaded] com.google.keystone.daemon.plist Support
  [loaded] com.microsoft.office.licensing.helper.plist Support
  [loaded] com.oracle.java.Helper-Tool.plist Support
  [loaded] com.oracle.java.JavaUpdateHelper.plist Support
  [failed] com.sophos.intercheck.plist Support
  [running] com.sophos.notification.plist Support
User Launch Agents: ℹ️
  [loaded] com.adobe.AAM.Updater-1.0.plist Support
  [invalid?] com.wacom.SketchManager.plist Support
User Login Items: ℹ️
  Google Notifier ApplicationHidden (/Applications/Google Notifier.app)
  Dropbox ApplicationHidden (/Applications/Dropbox.app)
  Adobe Creative Cloud Connection UNKNOWN (missing value)
  GoFlex Home Agent ApplicationHidden (/Applications/GoFlex Home Desktop Applications/GoFlex Home Agent.app)
  CrashPlan menu bar UNKNOWNHidden (missing value)
  EpsonRegReminder UNKNOWNHidden (missing value)
  CrashPlan menu bar Application (/Applications/CrashPlan.app/Contents/Helpers/CrashPlan menu bar.app)
  SophosUIServer Application (/Library/Sophos Anti-Virus/SophosUIServer.app)
Internet Plug-ins: ℹ️
  o1dbrowserplugin: Version: 5.38.5.0 - SDK 10.8 Support
  WacomNetscape: Version: 2.1.0-1 - SDK 10.8 Support
  OVSHelper: Version: 1.0 Support
  Default Browser: Version: 600 - SDK 10.10
  WacomTabletPlugin: Version: WacomTabletPlugin 2.1.0.2 Support
  AdobeAAMDetect: Version: AdobeAAMDetect 2.0.0.0 - SDK 10.7 Support
  FlashPlayer-10.6: Version: 15.0.0.189 - SDK 10.6 Support
  DivXBrowserPlugin: Version: 2.1 Support
  Silverlight: Version: 5.1.10411.0 - SDK 10.6 Support
  Flash Player: Version: 15.0.0.189 - SDK 10.6 Support
  QuickTime Plugin: Version: 7.7.3
  googletalkbrowserplugin: Version: 5.38.5.0 - SDK 10.8 Support
  iPhotoPhotocast: Version: 7.0 - SDK 10.8
  SharePointBrowserPlugin: Version: 14.4.5 - SDK 10.6 Support
  CouponPrinter-FireFox_v2: Version: Version 1.1.6 Support
  JavaAppletPlugin: Version: Java 7 Update 67 Check version
User Internet Plug-ins: ℹ️
  CitrixOnlineWebDeploymentPlugin: Version: 1.0.94 Support
  WebEx64: Version: 1.0 - SDK 10.6 Support
  Google Earth Web Plug-in: Version: 7.0 Support
Safari Extensions: ℹ️
  Pin It Button
  DivX Plus Web Player HTML5 <video>
3rd Party Preference Panes: ℹ️
  DivX  Support
  Flash Player  Support
  Growl  Support
  Java  Support
Time Machine: ℹ️
  Skip System Files: NO
  Mobile backups: OFF
  Auto backup: YES
  Volumes being backed up:
  Macintosh HD: Disk size: 748.93 GB Disk used: 674.07 GB
  Destinations:
  2 TB Seagate [Local]
  Total size: 2.00 TB
  Total number of backups: 7
  Oldest backup: 2014-06-23 02:35:59 +0000
  Last backup: 2014-11-08 22:08:28 +0000
  Size of backup disk: Too small
  Backup size 2.00 TB < (Disk used 674.07 GB X 3)
Top Processes by CPU: ℹ️
      6% WindowServer
      6% mds
      1% launchd
      1% sysmond
      0% GoogleTalkPlugin
Top Processes by Memory: ℹ️
  241 MB ocspd
  225 MB com.apple.WebKit.WebContent
  223 MB Safari
  155 MB WindowServer
  146 MB mds_stores
Virtual Memory Information: ℹ️
  932 MB Free RAM
  3.88 GB Active RAM
  2.39 GB Inactive RAM
  1.39 GB Wired RAM
  2.44 GB Page-ins
  16 KB Page-outs

Answer 1

When you have the problem, note the exact time: hour, minute, second.  
These instructions must be carried out as an administrator. If you have only one user account, you are the administrator.
Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Console in the icon grid.
The title of the Console window should be All Messages. If it isn't, select
          SYSTEM LOG QUERIES ▹ All Messages
from the log list on the left. If you don't see that list, select
          View ▹ Show Log List
from the menu bar at the top of the screen.
Each message in the log begins with the date and time when it was entered. Scroll back to the time you noted above.
Select the messages entered from then until the end of the episode, or until they start to repeat, whichever comes first.
Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message by pressing command-V.
The log contains a vast amount of information, almost all of it useless for solving any particular problem. When posting a log extract, be selective. A few dozen lines are almost always more than enough.
Please don't indiscriminately dump thousands of lines from the log into this discussion.
Please don't post screenshots of log messages—post the text.
Some private information, such as your name, may appear in the log. Anonymize before posting.