) They use triple the amount of buttons a Rogue uses.
See, I play on my laptop with a Logitech M515 mouse... Need to be able to pull magic off with these, is it possible? :P
Wrong, purely up to the players conceptions and needs.
I have played at a constant 2-2.5k rating since the start of arenas (up until s9, but thats another story) and I have only ever used a mouse with left/right click and a scroll, there is no need for an absurd amount of binds. Just use the area around your left hand with all the modifiers and you should be fine.
2) They seem "clunky" in their gameplay...
No sprint or mobility other than a rather limited and hard to use teleport..?
They don't have the escape mechanics of a mage, nor the shields of a mage, but they have Soul Link (which isn't really much of a substitute considering it doesn't actually remove any damage, but just shifts it onto your pet which can cause trouble through it dying if you are trained) and the teleport.
Teleport isn't hard to use at all, just remember to keep it refreshed in a good place if you are moving around a lot.
I can't answer the third question because I've only ever leveled one lock, and that was back in Vanilla.
But just remember to keep kiting and..well..be a bastard as much as possible, just kite and LoS and get the kill, forget 'skilled/style kills' and all that stuff, as long as the enemy ends up dead and you are alive it is a win. The control and finesse can come later when you are used to the class/spec.