To my knowledge, the holy Trinity was never "needed" in CoH. Mind you, I started in i6, so I don't know about the early days, but with the exception of fringe content, healers always took a back seat to (de)buffers, which is not the way a Trinity game works.
Additionally, and someone who was around before me can correct me if I'm wrong, controllers used to be able to lock down every spawn with their AoE hold, then Jack decided people didn't like playing City of Statues and AoE holds got their durations and recharges nerfed.
Tankers used to herd entire maps, that wasn't because of healers.