So, bountiful sunlight actually isn't useless at all. I see comparisons being made to heal/etc. This is a false comparison, bountiful sunlight is a regen spell. Yes, heals are more cost effective, but that's besides the point, it's a regen spell that'll give you hp back as you fight whether pve or pvp. It's like saying "why use sunlight spear? Just use lightning arrow.", because they're different and have different applications. Bountiful sunlight is usrful in co-op, for giving everyone and yourself really fast regen. You can also use it as a passive regen (while the team is idle or progressing, regen in the interim and heals in battle). It saves everyone estus.