I light my WSM (with or without pan some days) with about 12 lit briquettes. I think you're using too much lit. A WSM without a water wan/diffuser is pretty much the same as a UDS. Start it lower and try easing it up.
I just finished a UDS tonight and will be firing it up tomorrow. For a diffuser, when desired in it, I bought a clay pot base. That's all I use in my WSMs as well. Don't need water, it's just there to even up the heat, but I don't like refilling. Clay pot, like a pizza stone, does the same thing.
Neil -- "Easy Bake Master"
NB Bandera [gone to heaven...conveniently located in Long Island, NY]
Rebel 23, WSM A, WSM B, UDS, Easy Bake Oven
Pork Pistols BBQ
MOINK...It's what's for linner.