If it's percentage based I don't think it's going to change much, I think on live lava ticks for ~10% of your health now (correct me if i'm wrong on this, haven't swam in it for ~3 years) and in vanilla it was ticking for 500-600 damage which is anywhere from 10-20% of your hp as a fresh 60 with 3k+ so if it's the same as live it would actually be a nerf, can't comment on the lava jumping until release though.
The technique for doing it was using auto-run in the lava then just mashing the jump button so you saw pretty much 0 swim animation frames bunny hopping though the lava.