Insert the name Jax or Xin Zhao or Wukong and you just described these champions too... I haven't had any problems playing against a bad Irelia, but a really good Irelia is going to dominate you. Every champion has their power spikes and Trinity Force is theirs. Once they have it, you are at their mercy unless you are ahead of them in farm or kills (or both). Most bruiser top laners are like this. You really need to focus on not letting them roam to get kills, not giving them free kills in lane, and finishing out kills when they are low to deny them experience and farm. Irelia's passive means that as a top laner, you are at the most advantage when you are taking her down one-on-one, so you need to just focus on getting ahead of her. Don't let her farm without consequence. Don't feed her bonus kills. Push your lane into her tower when she backs to the fountain and deny her experience.
If you are letting an Irelia get a Trinity Force and you want to talk about her building a sated devourer, then you are doing something wrong. There is no way that an Irelia is going to farm out both of those items in less than 25 minutes (or even 30 minutes), especially if she is stuck under a tower farming minions. She will pick one or the other, but she won't get both and she won't get to keep her towers if she picks her jungle item. If she is building her sated devourer in lane, that means she is at an extreme disadvantage in the damage department and you should be winning trades against her anyway. When she roams into the jungle, take her tower. When she roams down the river, follow her and deny her the scuttlecrab (or an attempted gank on mid lane). If she teleports to bot lane, follow her, deny her a kill (or assist), or take her tower. Her ganking potential when she is building her devourer is negligible and the only advantage she might have over bot lane is that she has a level or two up on them (and only if you aren't denying her experience).
The champion is "fine", but when you find someone who really weaves her stuns with her trades well, you are going to be in for some hurt. But punishing a good Irelia player by nerfing her isn't really "balanced". She actually is in a pretty good spot. You just have to understand where her advantages are and where you can create your own advantages.