IMO tactics as they are now are just fine, for the most part. But yeah, people have come to learn to abuse them, switching tactics on a turn-to-turn basis. That's why I suggest a tactics-activasion delay. Falling prone takes time - switching from fierce aggression to jumpy cowardice takes time, too. I don't think there's much sense, however, in having any casual tactic be a draining task. Aggressive is effectively, the way I see it, not so much a straining activity as it is a mindset, gaining a good aim and a quick trigger in favour of hazard awareness and reactions to them. Coward's the opposite, and Cautious is a blend of the two, and therefor no less draining. Also, I don't think adding an energy counter to the lot will be in line with the direct, simple nature of DoomRL.