I agree it is not that powerful.
1. There is no target dropping, as hard targeting is not necessary (although possible). You are still in the same place an get hit like before.
All you can do is "walk away" but you will eat those AoEs everybody will drop as soon as someone vanishes right before them.
2. that easily doubles your magicka cost for those skills. Maybe worth it, maybe worth more just to use said skills twice.
3. You clear one dot, have no idea which one, hav no real UI showing you which dots affect you and how much damage you take from them. Really many skills add at least a meager Dot.
4. +15% stamina regen is a joke (at least at lower levels, might change, might not...) 15% @lvl 10 was 1 stamina per scond while at hardcapped regen rate. While skills cost what...40? 50? stamina.
+armor and +spell ressi might be worth it but my biggest concern:
It is not about how good the cloak is in itself.
You have to compare it to every skill you did not take on your skillbar so you can have it OR you have to compare it to every other skill you could have cast with said magicka.