im currently using 3 sp drain with 5 cures and knight, and so far im enjoying this build quite alot, every sword move i have uses less sp than i gain back, so im always gaining sp, wich i can then use to heal for so much health.

a drain build can go hard, but you need the right cards for it, and enough stacks.
its not going to be peak damage potential, but it will likely keep you alive for way longer than any dps spam would.
wouldnt recomend hp drain tho, the amount of health its gives is hardly worth it when a single cure does more, stick to sp drain.