I try to do that daily that gives 150 eyes in the Dalaran Sewers whenever I see it, and I also spend a bit of time fishing. On PvP nights whilst waiting for battlegrounds I would hang out with Sev and Shab and kill people (or I'd see Exray down there and he'd smash people) but it's a slow process.
You can't carry more than 5000 eyes at one time, so you might as well spend them buying things that make MORE eyes. Using the wand item on a boss makes them bigger and harder and also makes them drop eyes.
So if you want to get your eyes, go get a bodyguard and go fish, and kill the bosses that spawn. Leave the chest opening unless you want a bullseye on your head.
Anyway, last Friday I finally managed to fish up the last few eyes for my achievement!
And all for this! I love rats and having a ratstallion is just awesome! Ultra had his ages ago and I remember being so envious of it. I do wish the special of it was a rat eating, because that looks so cute.