Right now I think DK is probably the best for that, simply because they cover two elements pretty well. You could couple that with a restoration staff (healing for "water").

And it's an MMO. Keep zone chat on and you'll get all the air you'd ever want. ;-)

A DK with lighting enchanted weapons or even dual wielding lighting and frost enchanted weapons may be something you are interested in?

i had the same idea to build an elementalist.. although after a while of thinking i came up with this... Sorcerer is the class you pick because u gain access to storm call and use a finisher like mages fury which in my opinion is air. then dark magic offers up the crystal shot which is almost like ur gathering up rocks and shooting or using the 4.5 sec snare which looks like the earth came up and grabbed them. now u use an ice staff to get access to the water elements and i preferably use impulse because its one of the best destro staff skills. and for your fire element u use the maages guild fire rune which i morphed into volcanic rune. 5th slot skill i usually run magelight for crit chance or u can run the sorc teleport so u can escape. ultimate u can choose whatever. but this basically uses all the elements and ive fallen in love with how i use it. ill give u an idea for pvp how i use my skills.

first i start with encase( dark magic looks like earth) immobilizes enemies. then ill throw my volcanic run on them and either teleport in with bolt escape or just run up. then i use impulse a few times good chance to snare and the 10% reduce health is nice. then if the get low enough health ill spam mages fury or ill repeat my skill use. these skills all have great crowd control which is how many fights are won in teso. the only problem u have with this build is healing which i run destro resto staff and i cover healing with resto staff. if u are in need of a heal immobalize stun or knock up ur opponent and switch.