I agree with CaptTastic.
The sweet spot for Sentinels for me has been the smooth power curve from 1 to 26 so far.
Most of alts go like this. After reading some glowing build description on this forum.
1-15 Easy enough
15-20 Start to notice the lack of status protection or squishy-ness in melee because of under slotted powers
20-30 My damage/defense sucks and I cannot get the right IOs. Actively avoid mobs that mezz with squishy heroes
30+ Alt-itish kicks in because the slow grind due to enhancement costs. Realize that the char will only be god like once I get to 50 and have god like IOs sets
Too many builds, that are god like at 50 with IO sets, are very painful to level until then. This is common problem in MMORPGs.
My Fire/Rad Sentinel has been very different. In my 20s I am satisfied with my powers, damage, and defense. I actually seek out Tsoo and Lost because of my mezz defenses. I look forward gaining new powers that will change my play style, but happy with my current powers. I can pump out damage at a steady pace in groups and have been one of the few survivors in bad pulls while still actively fighting instead of running. It is possible that I do comparable damage to others over the course of the whole mission because I am always firing and rarely worrying about health. Very hard to prove. Also, I will pull mobs off the other squishies because I know I can take the hits.
In the end, my hero will not be as powerful as a full slotted level 50 god build, but I am enjoying the journey a lot more.
Unless the Sentinel powers get some kind of serious boost of course. Then I will have the best of both worlds.