Burn is seriously TOO overpowered against the raid boss. I've taken off over 30% of it's hp with just about 15 energy because of burn, which deals 99999/turn to it. Also, strength curse is also overpowered against it, causing it to hit my team for less than 100/hit.
Gabriel is about 10x harder than Veigraff as a boss, but once you use her as a mercenary, she's only marginally better than Veigraff is, to the point that I actually contemplated keeping Veigraff instead of swapping her in. A lil' buff would go a long way, to better keep up the illusion of her being an end-game merc.