one big simple tip i can give you: Respec shadowheart. literally just pick a different type of priest. maybe knock her strength down a little. i like life domain, but plenty of the others are good too.
otherwise, just try to play with the environment more. be ok with not hitting the enemy sometimes. hide around corners and behind doors, shoot from high shadows, use the area of effects as well as you can. sometimes you can cheese the hell out of fights in ways the game encourage.
all that said, paladin starts week, shadowheart’s default loadout just IS week, rogue starts week, and with wizard you gotta find the spells that work for you. some of them are bad and the class starts with so few spell slots…
try getting the staff from the waukeen’s rest quest reward, the amulet of magic missile from blurg and like a couple other “lightning charge” items and give all that to gale and start spamming “magic missile” you’ll feel strong.