Not safe enough for HC I'd say tbh e.g. for cow running she can easily handle mana burn because they're melee, but in the Pit you have those nasty ranged archers. Having played her a lot, by now I feel I've improved running technique enough so that I rarely die, but she can't avoid deaths altogether long term I'm afraid. You can go hundreds of runs without any issues, but at some point a couple of arrows from a Fana/Mana Burn pack will hit you, and if you're cursed on top of that.... RIP before even realizing what's happening. ES is definitely way to go though, the vita build is much squishier.