I think the duration of the skill is still taking invisibility into consideration as a 3 second minor protection buff is quite awful especially considering the skill costs 3700 magicka.
Its impossible to constantly cast this skill for somebody trying to play a different nightblade style and the heal is too low for PVP imo but I suppose thats up for debate.
Compared to the 20+ seconds Wardens get for minor protection, NB's dark cloak should be buffed to around 10-15 seconds imo and the heal to be adjusted too.
What do you think nightblades?