The best spec for leveling is defiantly the ice spec!
A theurgist doesnt need any dds for leveling - just use ice pets, they are cast-pets and does spirit-damage. Good damage,especially if you kill spirit vunerable or even neurtal mobs. There are plenty of them in Alb - all undeads, lot of mobs in Barrows, Lyonesse, Corwall, Salis, in Frontier.
For an ora-con mob are only 3 ice pets needed, so you still have 79% of power after that. For secure hunting - 4 pets.
In each other skill you will need more power and therefor more time/xp.

Even to grab a single bubble from the eath line isnt necessary but it gives you a security-feeling and could help against the adds.

After lvl 40-45 a group will await from the Theurgist a bubble for hunting in DF, Dodens, for other lila mobs and bosses. So, could be usefull to respec to at least 26 or even 35 eath.
But also in full ice spec you still valuable for every group as a root-puler, and pet-caster for to-hit and dd-caster.

Wind sounds good,but:
1. the last damage spell is only lvl 45, it means resist quote will be higher, then with lvl 50 dd (both - specDD and the base one as well) from the ice line
2. Pet-proc for stun from wind pets shouts too seldom to be a relationale
3. Wind-Pets lives too short - 20 sec. and could be killed just with one dd, ae-dd or bomb, they have less TPs,then other pets
4. ae-mezz is too short and just switch on the resisttimer for mezz, if you are in group with sorc - leave him this job.
5. dd costs too much power for leveling - you will need plenty of power pots for soloen or a group with sorc, mins or necro.

Eath is only for PvE raids good. OK, for taking keeps too.
For leveling it is nothing - high bubble eat too much power, eath pets are not able to kill higher mobs then yelow con solo, they are melee, so, they get add on spawns, you will need lot of them for hunting -> to high power use.

And also for RvR is eath - worst skill. I played hibs and could say - eath pets are not a point for rvr - each hib group has a bomb, just onbe cast and all you pets are down. Each mid group has a runi with ae-dd - one cast and all pets down as well.

Best Endskills are:

1. 45 Wind 25 Ice 10 Eath or 45 Wind 26 Eath 14 Ice
2. 50 ice 20 Eath
3. 41 Ice 35 Eath or 40 Eath 36 Ice