If your emotional state ... causes you to act in ways which do not reflect your evidence-based assessments, it is causing you to act against your rational decisions and is therefore irrational.

So, anything which decreases rationality is irrational? Sounds like circle reasoning to me.

Besides, you original point was that

An emotion is irrational if it is not appropriate to the situation

If I wake up in a burning house, fear is certainly appropriate to the situation and yet it's very likely to decrease the rationality of my decision-making. If I'm making out with someone I like a lot, love/tenderness is appropriate to the situation and will decrease my rationality. Etc. etc.

This starts to remind me of a steel Vulcan :-)