A non-Halfling melee rogue would need to be able to disengage, move away, hide behind some sort of obstruction, move back and then attack from hiding again to use assassinate again. A feat that is simply very hard to do(and not really worth it in most cases.
It would be far easier just to stay near a ally and sneak attack, bonus disengage, move away. Then use partial move, sneak attack, bonus disengage, partial move away. This way they could use sneak attack every round and not face return strikes unless the enemy closes with them(hopefully drawing attack of opportunity from the rogues ally).
So far Halflings are just amazing rogues in two regards.
Halfling can hide behind fellow party members as well as move into and out of med sized enemy creatures spaces(this ability combined with (bonus)disengage lets Halflings move through enemy combatants without drawing attacks of opportunity).
Keep in mind however that disengage by itself provides no movement so they can still only use there normal movement for all their movement needs!