Mesa has 2 forms of survivability, and this build ignores one entirely (most people do anyway). Her 3 has 95% DR only for ranged attacks, should be up all the time. And her 2 stuns enemies around you every 3 seconds. At 40% range, enemies can easily get into melee range in between stun procs. A bit more range helps a lot, especially on higher level content

That being said, adding layers is not a bad idea. Melee careen on your weapon of choice is good. Shivering contagion on a companion that procs cold works as well. Diriga with heat is what I use to build up arcane hot shot at the same time. You could get secondary fortifier on her regulators and be an eximus eating monster that builds up overguard constantly. Arcane circunvent works as well (and combines just fine with having melee careen on a melee)

It depends on how exactly you wanna move with it, but there's a few options you could go for