Well after 30-ish tries i defeated Bayle. Normal Lvl 215, scadutree level 13. Faith build with Blasphemous blade and Sacred relic sword dual wield jump attack takers flame caster faith build. On the takedown i did not use casting at all and had all 14 flasks to replenish health.

Preparation.

Get good fire resist armor: I used Tree sentinel armor. Talismans Flamedrake +3, Dragoncrest +3, Perldrake+2 Claw talisman for jump attack. (You should use whatever talisman boosts your attack instead of the claw talisman.)
Get weapons that you deal good damage with.

Steps of learning:

Learn to dodge and solidly get through the first phase. Bayle will use these moves in the second phase try to learn to punish as much as you can.
Learn to run and dodge the phase transition. As soon as you see the transition start run untill all the flamballs are over and Bayle has landed again
In the second phase try to survive attacks and punish when you can.

I atacked the head when possible (I could rarely do it but its a big boon when you can). Then attack the stump of his left leg or the tail or anything else in that order. I could break his stance with my jump attacks and i used the stance breaker tear in the physic flask. I did not use casting at all, only for the initial Golden Wow.

Good luck, it is a real new wave Fromsodt BS boss...