Pretty sure she can 100% armor strip now. She got a tune up a while ago

Mag is insanely strong but lots of people just don't read her kit. I certainly didn't for a while until someone said Mag was shit... So then I checked out WarframeFlo's video on her and realised she melts everything if you play her correctly. Just capture any enemy you want in a magnetic bubble and any other enemy who walks into the bubble, just disappears in a swarm of bullets. The bubbles stay for quite a long time too, and you can make many of them. Another skill just leaves shards of shrapnel or something that also dissolves enemies around the map. Pull is fairly useless if you aren't host, so switch that out with Nourish or something. And the other skill is a decent emergency offensive skill which restores all your shields instantly. She most likely does more that I didn't mention, but that's how I understand her kit and I always have fun playing her.

If your weapon is weak, she might not be so good, so use an incarnon weapon or a weapon with lots of multishot etc.

Probably not as useful with some bosses maybe, but I try to avoid warframes shitty bosses for the most part.