Why? Seriously why the Heck should the gm be responsible for throttling ADEU style encounter powers in a long rest based adventuring day based system with "you should be able to take one every encounter"? If something should be at will it should actually be at will or get tied to a trigger throttled by the rules themselves (ie like the rolling initiative stuff). If something is too good for at will, the relevant class needs to be designed with a long rest based fuel tank &power scale".Somewhere in the 5-15 minute range. The important bit is that you should be able to take one after every encounter unless there's a very strong time pressure. Whatever it is, it's probably a good idea to scale other things that use non-combat time (e.g. rituals) to use the same unit. And most classes should have a significant number of things that recharge on a short rest, or at least have the option to do so. For example, casters in 13th Age get a certain number of spells per level, but the spells themselves can be either at-will, per-encounter, or daily, so you're encouraged to choose a good mix of them. Another nice example is the CRPG Divinity: Original Sin 2 (I guess 1 was similar but I haven't played that) where "skills" are balanced by having cooldowns of 1-5 rounds, so you can use them multiple times per encounter but not at-will.
The whole thing of attrition over the course of an adventuring day can and should go away, or at least be minimized.
This "it's too powerful for at will and the gm is at fault for not designing the entire adventure around throttling it hard enough if it becomes at will" is not at all reasonable design