Personally, whether Horde or Alliance, I can't imagine not having a Warlock for any dungeon focused team that includes a main character that frequently goes off to do other content (raids, battlegrounds, etc).
Well, when leveling you always log out at an inn so summons is not needed. It isn't even workable unless you have summon alts since you need 2 other party members anyway. You always set the hearth stone to the town nearest the dungeon. For Horde, Brill is a short run. Then you go ZF and gadget is a short ride. After that you just grind to 60 in BRD and either base in Kargath or Undercity (portals and thorium point).

At 60, it would be nice to have a summon team for Strat as that takes forever to fly to. But usually my whole team just travels together for world buffs anyway.

I am considering a new lock team, just for something different and for some reason there is a dearth of locks on my server i.e. easy raid gearing.