I'll bite. not wanting to come off as snide but it kind of makes me curious what you've been doing for 75 levels. what your skills do/are and a solid rotation is something that should have been figured out awhile ago. Are you wanting to blow things up really quick or do you want them to bleed to death?
critical response skill damage
subtle stab damage multiplier
subtle stab critical(this is optional but you're going to be using this skill alot)
positional surprise strike
feint attack cooldown(if quiet knife)
lucky strike cooldown(if gambler)
quite a snag(if mischief)
mischievous glee healing
glee pulses(this is optional and many burglars feel differently about it but I loved this legacy)
addle induction multiplier
skills critical multiplier
you have other legacies left that you can choose, what else you want is up to you but like I said, you should already have had a plan as to what you were doing and how you wanted to build your character.
a familar rotation is location is everything, surprise strike/cunning attack (from stealth), counter defense, critical chain-burglars advantage, double edged strike, aim, generally flashing blades should follow this and if thats what you use, use addle to interrupt the animation, exposed throat could also be used here, then you could pop a trick, use feint attack and go through your critical skills again. I used subtle stab inbetween burglars advantage and double edged strike.
hope this helps