While I was leveling my Nightblade I didn't notice because the number of Daedra/Undead (and maybe Werewolf, with the Fighters' Guild passive) was very low, at least, when they were fought at once.
Now, in Coldharbour, playing with Camouflaged Hunter (or its morph Expert Hunter, in my case) causes a huge FPS drop when there is more than one around me. It's so much lag that while soloing "The Village of the Lost" a few minutes ago, I couldn't even block the heavy attacks because I couldn't see the enemies performing them (the yellow sparks indicating something stronger is coming).
It drops so much that is noticeable that the reason of this lag is the auto-refresh effect. IMHO (and I keep this as a suggestion) the effect should not be applied every time you kill a Dadedra/Undead. Instead, wait for disengage combat to do so. Good example: If you're surrounded by +/- 10 Daedras, like taunting both groups in the area after the first bridge/passageway in The Village of the Lost, and start spamming Steel Tornado all around you can almost see the fight in slowmotion.
Don't have the effect of the ability activated for 1-2 seconds isn't that damaging as being unable to see what's coming after you. And even if it would, without this lag, 80% (or more) of the enemies around you would be dead already, so you could escape/regen/hide/whatever
I am the very model of a scientist Salarian, I've studied species Turian, Asari, and Batarian.
I'm quite good at genetics (as a subset of biology) because I am an expert (which I know is a tautology).
My xenoscience studies range from urban to agrarian, I am the very model of a Scientist Salarian.