Enjoyable all round - maining the flame gives a nice spread of situational options to give you the edge once you have enough ammo, and bringing three Fire Storms to a boss fight is great fun.
Not sure if the DEX cast speed bonus is worth building around - it's somewhat noticeable and probably saved a few tight situations, but Combustion is already fast enough and Fireball is still too slow to insert manually.
But good lord, Gwyn is such a car crash of a final boss for a no-poise build. Manus? Fine. Kalameet? No trouble. Dark Anor Londo Gwyndolin? Bastard of a runback, but a fun gimmick to unpick. Gwyn? Pure hitbox rushdown CBT.
Tried everything I could think of save for straight grinding, and the only winning strat was meta capitulation - tactically deploying a half-Havels and Ring of Favor and Protection to claw back enough margin to burn him down. Pah

In the end, noted arsonist Arthur Brown of Whitby - who looked more like Bruce Dickinson of Worksop, but what can you do - incinerated the world by hand, and is still at large. Word is he's working on a comeback album.
0/10 shit game. Can't wait to replay it again as a rush-lordvessel holy hammer paladin.