well IMHO TK rankers are there for the challenge, and their extended HP and SP is merely to allow them to chain more hits. The infinite kicks is basically just for fun button-bashing and to increase DPS.
SGs are in no way underpowered. I would even dare say that all-round SGs are the best extended class there is...
Monkey, you seriously gotta learn to count your blessings. Limits are there for a reason. Limits are there to challenge yourself. If you don't want limits then go to those high rate high level high stat servers that don't upgrade their mobs...