They're a bad idea since it takes two feats just to eliminate the ranged "in melee" penalty, and wizards already have bad hit rolls. And the effects of most of these spells, like melf's acid arrow are often equaled or out-done by magic missile which never misses and is a lower level. I prefer using only saves to "dodge" spells. As for the bugbear fight, the AI surprised me by ignoring and running around my meat shield dog and crit'ing the enchanter for some kind of absurd damage.
You may need more than one meatshield, but there's definitely a way to block the chokepoint. Also, if you get initiative (or even sneak in, go in invisible etc.) and kill/incapacitate the bugbear who runs for help, you might avoid bringing those bugbears into the fight.
I find Spiritual Weapon the best choke point summons, and as long as you stay away from that doorway, the bugbears won't know you are in the other room. They completely ignore the dying screams of their comrades and all the sword clanging going on. Maybe this is is a job for Sitra to create a "reactive Bugbear room', where the leader Bugbears come out of that room once the fight starts, so instead of 2 half battles, its one big fight.
It is a great meat shield, but in my case it's a cleric spell so no luck. My second try on the bugbears went smoothly, managed to keep them under control with the buffed half-orc and summons. 1st level was ridiculously hard, but now at 6th level, they're dropping almost everything effortlessly. The battle against the huge frog outside nulb was without a hitch. As long as they can rest, they're a wrecking machine now. No rest, and they'll be lucky to survive a second or third battle in a row.
It's already "reactive" - the melee bugbear in the first room triggers the second room. Of course, players like us who know that like to exploit that and kill the guy asap. A new player wouldn't know to do that. IMO, this is WAI.