Mesmer and Elemental builds

I really enjoy the PvE portion of the game, I do want to go into PvP one day, but with the skills that I choose. Anywho, onto the point.

I love the mesmer and I want to try the elementalist. So, I have two builds I am thinking about:

Mesmer/Ranger
-Focus on Illusion and Beast Mastery.
-Can't decide on another skill set, maybe Wilderness Survival/Domination.
-I like the DoT from Conjure Phantasm and Phantom Pain would only add to it
-I won't take off Beast Mastery cause I love having the pet and it was the only reason I picked Ranger as secondary.

Elementalist/?
-Focus on Earth magic and energy storage.
-Secondary class may provide other skill set.
-The first time I read about the Ele, I loved the idea of Earth magic.

So, my question is: are these builds effective in PvE? Also, I would like some suggestions for my elementalist's secondary class.

Thanks in advance.