Unless you're in a hardcore progression guild (i.e. in the race for World-First boss kills), you should always just play whatever spec you enjoy most or are most comfortable with. If you find yourself under-performing versus other DPS at your gear level, it's because you're either a) not geared correctly and are missing vital set-pieces (tier bonuses, trinkets, legendary ring) or b) you aren't playing your class correctly (wrong talents/glyphs, or you aren't following your spell rotation to the T).

I would recommend re-reading the Icy Veins in-depth rotations word-for-word and making sure you're doing exactly what they say -- one reason you aren't doing enough DPS could be because you're accidentally prioritizing one spell over another, you're casting Earth shock too soon or too late, etc.

Once you've made sure you're following a guide exactly, another fairly simple way to improve as a player is to get an addon to help you with your spell rotation. If you haven't used Weak Auras before, I recommmend you download that addon and look up a good T18 Elemental Shaman weak auras collection. This will help eliminate a lot of the guess work with playing Elemental. Even just casting Lightning Bolt at the wrong time is enough to reduce your DPS by 20% or more, and a good Weak Auras string up will help you prevent that.

Don't give up on a spec you enjoy just because you think another one may help you numbers-wise. Do your research and try to improve as player, and--at least as a shaman--you'll probably end up doing your best at whichever spec you have the most fun playing (even if DPS rankings say another spec is better). I've played Enhance for a long time, and I've always found I do better as Enhance even when guides say Elemental is the better option, just because that spec "feels" right to me more so than Elemental does. If Elemental is the spec that feels better to you, then that's probably the spec you'll perform your best at, provided you're playing it correctly. Hope this post helps!