Anyway, what I mean is, why NOT telegraph that information? Why not show that the fire archon is beginning to well-up with flame from within, or that the sniper has pulled another of those wickedly barbed arrows? It allows the players to act and think accordingly.
Maybe the fighter with the defensive shield moves to his bloodied ally and activates his powers to boost defenses against ranged attacks. Maybe the guy with fire resistance bull-rushes the archon backwards so he can't get near someone for a big attack?
Personally, I like the idea of telegraphing things like that... It adds to the encounter, because the characters can see and know things will happen if they do not make moves against it, rather than just repeatedly surprising people with something they had no way to defend against.