Guild Wars 2

When I have facet of nature active, I can not use shiro impossible odds because apparently I do not have enough energy, although I sit at 50% (see screenshot)
What am I missing, is this a bug?

Energy regen is between +5 and -5. IO uses 10, so all of it. To activate it and F2 you’d need to run with -7 regen which is impossible.

This is definitely a bug, or intended but not noted anywhere. It seems you can’t go higher than -10. As you said it uses 10, not +5 and -5 ‘as 10’ (that would mean upkeeps using less than 5 regenerated that amount :-P ) and -7 regen is possible (-10 with IO or -8 with all upkeeps except elite).

seems like i didn’t think that through thoroughly enough. Please ignore what i just wrote..since i can’t delete it.