Unless I'm missing something, Hildryn, to me, is a contradiction of badass aesthetics and mediocrity on the field.
First off, why is the bodybuilder frame a shield-oriented user? Wouldn't it be more appropriate for her abilities to revolve around physical strength? That aside, most fall short in comparison to other frames and or weapons.
Balefire is no better than a secondary. In fact, I'd make an argument that most high-rank secondaries easily outclass it. Truly a waste of an ability. You could contend that its use comes in its synergy with Aegis Storm, but that's just a contrivance on DE's part. Why not simply allow us to fire our own weapons?
Shield Pillage is a paradoxical ability. On the one hand, the shield replenishment is a nice effect, on the other, by the time it feeds back to you, combined with its initial casting fee, it hardly matters. You'd have to spam it constantly for a worthwhile result. That and, if you run out of shield there is no "oh-crap" button to help you a la Inaros's health drain or Limbo's dimensional step. Might as well stay of the enemy's line of sight and opt for the routine run-and-gun method. To be clear, though, it's not bad, rather her best ability, but even it has some issues rooted in questionable design.
Haven does... something? I realize it's supposed to provide a cloak-like AoE around Hildryn and her allies but the damage is so low (unless I'm missing something) that what's even the point?
Aegis Storm is a cool ability, but it's no better than Vauban's Bastille. Worse yet, at least when it comes to the latter (a third, ability, mind you) you can fire your own weapons and not have to uphold the same position seeing as Bastille is stationary. Finally, we come back to low damage.
I'm sad to say that, at least for now, Hildryn falls under the "meh" category, a Warframe whose replacement with almost any other would prove an upgrade in a mission. That's such a shame since I find her aesthetically so pleasing and have enjoyed fashioning her so much. I hope DE would give her a boost in the future.
By the by, I would love to hear from someone who can make her effective. Share your secrets with me, oh wise ones.