Ok straight to the point: Magicka Nightblade is a jack of all trait, but master of none (in PvP only, they're still demigod in PvE). Yes, bombblade is extremely effective, but only in specific situations, and they're utterly useless in any others. So let's think of a way to make Magblade somewhat competent in every situations (you know, like almost every other classes).
My suggestion is simple: Give Magblade more survivability. The new spectral bow heal is a welcome change, yet it is way too unreliable (you know, it's a heal that require 5 light attacks beforehand). There are 2 changes I can think of, and I'd be happy to see either of these changes happen (I don't think we'd need both them, however).
1. Make Dark Cloak scales to either health or magicka, whichever is higher. This change will possibly give magblade a reliable heal but still avoid them to spam it like an addict.
2. GIve a buff to the healing from Siphoning Attacks. Either increase the amount it heals, or make it heals for x% of the damage dealt with the light/heavy attack.
Personally I'm not a magblade player, but I've encountered so many magblade with various skill level, and almost every single one of them told me the same thing about how their survivability is almost none existence. This is just merely a suggestion, and I'd love to hear other opinions.