Vigor loses it's effect quite quickly with lowered HP, it basically has no effect at half hp. It's mainly powerful for a nukeing scenario like a full burst out of the gate, be it from saving up like in a GO from the previous stage, or during burst time. Particularly if you have good healers or kamis that can negate damage. Obviously, not so great against content that constantly hammers you with damage. Still, it's worth noting again, the reason Vigor is so strong is because it's a separate multiplier, so it really can't be compared to normal additional modifiers. That's because unlike the others, it doesn't have diminishing returns as your grid powers up.

Pride is actually quite valuable because at around 70% hp (for Large Pride every 30% loss is another 6%), it becomes as good as a large assault, and keeping at 70% hp isn't that hard/dangerous as you get more and more hp.