fearsomepirate
Hero
Wizards are extremely dependent on prep and distance. A CR 8 wizard should be what, 11th or 12th level? If he's sitting in a 25' by 25' room and is inactive until the party opens the door, he's toast, because anything he tries to do will get Counterspelled, and he'll go down in a round from melee attacks. If he uses spells like Alarm and Arcane Eye to keep abreast of things, so that he's got his Globe of Invulnerability up when the party opens the door, or sticks a Cloudkill inside a Glyph of Warding, things could get very nasty, very quickly.