So I'll opine that some sets would only need one or two of their powers to also affect the user, and that's it.
It would be entirely balanced to help those sets stay abreast of changes over time with other sets that clearly are outperforming them in some capacity.
Clearly allowing every buff power to be self-affecting is entirely not balanced, but also not needed. As follows, here are my suggestions:
The sets that probably are the biggest candidates for a little self-buffing are the "shield' sets, such as:
Force Field
Sonic Resonation
Thermal Radiation
Cold Manipulation
All of these would benefit from a reduced-benefit 'splash' from their two shields. Perhaps anywhere from 33% to 50% value. And that's it. They don't need Forge or other buffs to be self-affecting, just give them some benefit from their shields and I think that would be balanced.
Some other sets that could also provide some minor benefit to the user are:
Kinetics - allow them to receive a partial benefit from their Increase Density.
Empathy - allow them to receive a partial benefit from Fortitude.
Pain Domination - allow them to receive a partial benefit from Enforced Morale and also make this power an AoE as with Kinetic's Increase Density.
Poison - allow this to get the same treatment as Trick Arrow (i.e. review those debuffs, and allow Alkaloid to be an AoE heal instead of ST or be an untargeted cone ala Nature)
The sets from my experience that don't need any self-buffing beyond what they might already do (or not):
Trick Arrow
Time Manipulation
Dark Miasma
Electrical Affinity
Nature Affinity
Radiation Emission
Storm Summoning
Traps
Just my 2 INF.