Do you not multidot on melee too?
Whenever I play my rogue, I put the finisher dot on multiple targets
On my pally I judgement different mobs when I can (with that glyph I think that makes it to more damage)
DK has dot spreading abilities, but sometimes requires dotting other mobs too far away when target switching
the list goes on... Multidotting is a part of WoW, and it is laziness to not do so.
Ele sham and hunter have the least multidotting of everything, try one of them but still expect to use dots
Frost mage, destro lock, ele shaman. Multi dotting is such a small dps gain with these specs (compared to aff lock and spriest etc) that the difference between multi dotting and not multi dotting isn't really that big a deal.
A frost mage on protectors spamming Nether Tempest and keeping it up on bosses and adds as much as possible, while doing the normal rotation, is doing WAY more damage than just using the single target rotation, so its a big deal and that's not the only boss where multi dotting is useful.
You can ignore it if you play just for "fun" but if you want to get in high places you gotta put some effort in learning how to multi dot properly.
Play a destro warlock. If you have 4 or more mobs, cast fire and brimstone and when you cast immolate it spreads to EVERY mob within a 10 yard radius, so that's two buttons that you press. Then while fire and brimstone is still up, cast conflagrate x2 and incinerate and you just BLEW the F UP 4+ mobs at 300-900k dps (depending on gear). Then before your target dies, cast shadowburn, get 2 more embers and BLOW UP anything else that isn't dead then continually gain 2 embers through shadowburn and crit for 400-700k on an instant cast.
destro lock, dotting does almost nothing, when we need to cleave, we can just havok chaos bolt adds, u also get an awesome tank pet incase u want to solo stuff, and u get ur own spellpower buff + battle res, and fort. plus you do great dps. ele shamans are good too, and balance druids.
Well 6.0 Patchlogs came out and they addressed the Issue of Mage being too DoT-y via the Bomb Talent in many ways so now you can pick Mage to be not DoTy. There is also a Talent Option for LV100 Shadow Priest that does not rely on DoTs, giving you the option to opt out of DoT-y Playstyles, except on Warlocks where all three Specs have some DoTs as Blizzard's Class philosophy.