The team setup in your OP does not apply to the majority of teams at 50. So any conclusions you draw from it lack a wider application. Sorry.
That said, your observations do apply to min/maxed level 50 teams. Which is where the conversation should focus IMO. (I.e. No suggestions for changes that will impact casual/regular/bad players. Such as buffing bosses, nerfing AOE, etc.)
Buffing mezzes...whilst making them miss more? Pointless.
Anyway, the problem isn't the strength of the mezzes. The problem is that the controllers aren't given the opportunity to mez in min/maxed level 50 teams when everyone is playing optimally. It doesn't matter if your hold is mag 3 or mag 5000 if your min/maxed level 50 team-mates are AOEing everything to death.
No-one finds the game too easy.
Some people dislike that others find it easier than they do, though.
But that's just your usual casual-player-whining-that-the-min/maxer-is-better-at-the-game rhetoric you find on all MMORPG message boards.
Anyway, academic. Not relevant to whether controllers needs buffing or not.
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While I'm still unconvinced that there is a surplus of AoE damage and that said surplus is a significant problem to the majority of non-min/maxed level 50 teams. (Outside of Judgement, which I consider to be one of the worst things ever added to CoH.) I can still see that controllers are probably due a buff that will allow them to contribute to the level 50 min/max meta. Controllers are one of the most popular ATs, and it's not fair they are left out.
Let's consider the current min/max meta at 50:
Damage
Support (buffs/debuffs)
Tanks (take the alpha, group the next spawn)
Controllers do Support already. Damage isn't their role. So maybe something that lets them "ghetto tank" with their primary would be the best way to fit them into the meta? Like so:
Controllers taking the alpha - Give controllers something akin to the blaster buffs - higher HP cap, more survivability, etc. (They will still be more squishy than tanks, but their controls should help mitigate this.) Although I'm worried doing this might start a slippery-slope for Defenders/Corruptors/Dominators all getting something like this.
Controllers group the next spawn - Give the T1 controller power the ability to "bunch" up a spawn. (Similar to how tanks do). It would work like this: You select one enemy in the group with it, hit fire, and the result is a reverse propulsion-field. Every other enemy in the group is drawn to the target for a second or two. (Long enough for the controller to get off their AOE mezzes.)
So while everyone is AOEing spawn one to death, the controller is prepping spawn two. Their bunching and controls helping to streamline the damage-train, much in the same way tanks play in the current meta. This would make controllers very welcome in min/maxed level 50 teams IMO. (And would also make them more useful in regular teams!)
Benefits of this idea are that it doesn't add to the AOE damage creep, it doesn't make the game harder for everyone else, and it doesn't nerf anyone.
Thoughts?