There are 2 main issue to solve in order to be able to run in dalaran lag free having enough memory and being able to load texture fast enough.

The memory issue can be minimized if yeh dont run at a super high rez with all affects minimized. I'm not sure what the cut off point is but if yeh want to play in high rez yeh have to have more memory which force yeh to go with a 64bit os I would say 6 gigs at minimum.

If yeh have enough memory or play at a low rez loading texture wont be that big of a deal it may cause some stuttering but wont be a game killer.
Having an ssd drive would reduce the stuttering.