Personally. I would revamp Character creation.
Instead of having 14 separate Base Templates that power sets are added to based on AT choice, I would have a single Baseline template, and was then modified by AT choice, then Power set choices.
That would allow for easier balancing between the power sets, and ATs themselves.
And example of the baseline template and an AT modification could be as follows.
Baseline template:
HP: 100
DEF: 0
RES: 0
etc...
The Tank Modification would be (numbers would most likely be different)
HP: x1.3
DEF: 0
RES: 20
etc...
Then the power-sets would offer their normal effects
Tanks would have more RES
Scrappers would have more DEF
Blasters would do more damage
etc...
This would free up all the Power-sets for all the ATs. (if the Devs so desired)(Also making the Sentinal AT superfluous)
That way, a Blaster could choose an armor set, a Scrapper (or Tank, Brute, Stalker) could choose a ranged attack set.
The AT choice would determine the base stats, so to speak, of the character, and not the entirety of what the character would be.
Tanks would still get punchvoke, scrappers would still get crits, Controllers would get better mez mag, Defenders would get better buff/debuff numbers and so on.
But, you could have a Blaster and a Dominator with the same power-sets, and they would play totally differently because of the AT stat modifications to the baseline template.