I play on a few noobier lower level characters in my spare time, and I like many other noobie low levels ****ing despise sins (probably the class most people fear in 1v1 scenarios) due to the whole Ima' go invisible, tele to you and shank yo ass ability.
But frankly if you take that away from them, they've got nothing. I don't see much of an issue with it. A sin can happily stand 3 steps away and just jump you from afar with DoS. You could be lkira's lvl and still not see one coming. That, imo, is part of a sins playstyle and should be rewarded for doing so. You need to be alert at all times to if a sin is wondering around on the edge of your screen.
What I think people are really annoyed about is that if you are a higher level than someone as a sin, you could be standing right next to them and they'd have no idea you're there. Literally no idea, as they remain invisible until hit or decide to hit you. In which case, you're just going to die if either A) the sin is kitted enough or B) has any other type of damage backing him up. Heck, if a cd on suns come in god forbid you ever get 2 or 3 sins jumping the same target together. There'd literally be no counter. (Hence why a few of CORE are spending the time boosting up sins, on the off chance Jamie is retarded enough to implement it) My god it will be fun. Wizz+Sin complete domination.
Sins need their stealth mechanic and their run-fast mechanic to combat the fact it's still easy to target you from range. Yes, you could argue a sin stacked with MR and swift feet would be broken to all hell, but RNG is RNG. Their whole class is RNG. They could resist those crucial damage hits and in return wreck your face, or they might not and die instantly. That's part of a sins playstyle. Frankly if you haven't figured that out yet, you shouldn't be playing a sin.
TL;DR stop moaning. Game's more balanced than you guys give credit for.