Macbook Pro incredibly slow/laggy

I have a Mid-2012 15" MacBook Pro running OS X (Yosemite) 10.10.2. It has a 2.6GHz Intel Core i7, 8 GB of RAM, and a 750GB HDD.

Over the past couple of weeks it has become incredibly slow, to the point that simple actions such as clicking on an icon in the dock have caused the spinning wheel to appear. As far as I can tell nothing significant changed around the time that this behaviour started.

There is nothing unusual shown in Activity Monitor: CPU usage is low and there is over 6 GB of free memory with no swap being used.

Some example of the degree of slowness are:

• Scrolling down the page on an already loaded page in Chrome – Spinning wheel for 30 seconds
• Clicking in text field on Github in Chrome – Nothing happens for 34 seconds
• Refreshing a page in Opera – Spinning wheel for 27 seconds
• Opening Calendar from the dock – 70 seconds for Calendar to open, no visual feedback
• Clicking to focus open Pages document – Nothing happens for 21 seconds
• Opening System Preferences and clicking Keyboard – Spinning wheel for 30 seconds
• Clicking on the File menu in Finder – Spinning wheel for 23 seconds
• Swiping up with three fingers on the trackpad (show Mission Control) – Nothing happens for 12 seconds
• Moving cursor down a single line in vim – Spinning wheel for 12 seconds

I have tried the following:

• Turning it off and on again
• Making sure everything is up-to-date
• Performing a disk repair
• Resetting the SMC
• Resetting the PRAM

Is there anything else I can try to fix this?

Edit: Unbelievably enough I somehow didn't think to check the logs. Doing so shows the following message occurring regularly. Does this mean that my hard disk is damaged, despite the fact that the disk repair claimed to have fixed any issues?

kernel: CoreStorageGroup::completeIORequest - error 0xe00002ca detected for LVG "Macintosh HD" (C9D97BC3-3A2E-405E-BE14-0E9B3FAD7A0D), pv 90103BF0-50B3-455D-947E-A020BC46F680, near LV byte offset = 161931108352.
kernel: disk1: I/O error.