What's with Valentine's hate really ?
She's far from being bad, for example Last Hope (because it's the one that I actually use):
Her attack is quite low compared to others, but it's balanced by the fact that her attacks hit a lot of time and that her Blockbusters hit REALLY hard and can be comboed freaking easily. Plus Valentine's unique capacity make it impossible for the opponents to get their life back by switching.
Plus, she has a ton of HP and as if it wasn't enough, can survive death and come back with half her lifepoint, and, since it's Valentine, she can revive her dead allies with Forbidden Procedure.
Also, being Valentine, she have her Countervenoms that can debuff ennemies, stun them or reduce their blockbusters gauge and that can also be boosted with Vial Hazard (Yup, in case you didn't know, Countervenoms take Vial Hazard effects if you don't throw the serringe AND the effect of one Vial Hazard add up to all Countervenoms as long as you don't throw that goddam serringe -for the last information I discovered that today-)
Also her charged attack is a dash, which is great since you don't have to put her dash as a Special move like Cerebella and it pierce the guard. Downside is: you can only combo it with some attacks. Upside is: it's mainly Countervenom and Forbidden Procedure, which allows to revive a character that just die and deal great damages or to put down the opponent's blockbuster.
Well, then there's her Heavy Regen that trigger once per fight for all allies and who sucks big time, generally you'll die before tasting that sweet regen (But eh, since it's Valentine she'll come back to life when it triggers, so it's good .... but only for her)
And if you get caught by an opponent that can mess with your Blockbuster Meter you're in trouble if you can't get out of here with an Explosion.
But in the end, she's a good tank with good combo that make for good damages and she is the only character that can revive allies (and deal a fair amount of damages if you hit someone along with it).