I've played my fire ele a lot and I've never been a big fan of casting double Meteor Showers. The only times I've really found it useful is for disrupting monk bosses, and there are much better ways to do that.
I think there's a bit of a misconception about just how uber Meteor Shower is. Sure, it does the most damage--but is it worth the cost of echoing it? After Searing Heat got a buff in the last balance pass I started playing around with it again and found I was more effective with it than I was with Arcane Echo. Looking at the numbers, I've been able to see why:
Meteor Shower is 3x119 for damage, so that's 357 total. Searing Heat is 5x37+42 (the 42 being from the three seconds of burning), so that's 227 total. Both cost 25 energy, but MS causes exhaustion and takes an extra 2 seconds to cast, so you're definitely paying for that extra damage.
The numbers for echo MS vs. MS+SH, then, look like this:
MS+MS: 3x119 + 3x119 = 714
MS+SH: 3x119 + 5x37+42 = 584
That's 130 more damage from an echoed Meteor Shower, but I find that a lot of the time, enemy mobs are able to escape at least one of the six meteors. While, on the other hand, Searing Heat only lasts five seconds instead of ten so I find enemies are almost always held within it for the complete duration. Factoring that in, the numbers are a lot closer:
MS+MS: 3x119 + 2x119 = 595
MS+SH: 3x119 + 5x37+42 = 584
That's only 11 damage less, and when you consider that 42 of Searing Heat's damage is degen and doesn't get reduced by armor like the rest, the MS+SH combo will probably even come out on top. So you've just done about the same amount of damage, in less time, and without as much exhaustion. Interesting, no?
But here's the real kicker: Since Searing Heat takes two seconds less time to cast, you have time for a Fireball on top of that while still staying within the same time frame as an echoed Meteor Shower. By then enemies are probably going to be scattering, so it probably won't hit all of them--but then again, you'll at least hit what you target, whereas the last of six meteors probably won't hit anything. So we now have:
MS+MS: 3x119 + 3x119 = 714
MS+SH+FB: 3x119 + 5x37+42 + 119 = 703
That combo is competitive even assuming that all six meteors from an echoed Meteor Shower connect, and it still doesn't cause as much exhaustion. As well, if you're using Archane Echo for the double Meteor Shower, it costs the same amount of energy; or if you're using Echo/Glyph of Renewal, it's only 5 more energy.
But that's not all. No, since you're not getting double exhaustion from two Meteor Showers, you can run Ether Prodigy without getting bogged down by too much exhaustion. That lets you spam Fireballs, Immolates, Rodgort's Invocations, or whatever without having to rely on an easily-stripped Elemental Attunement.
So, for the record, my fire ele build currently looks like this:
Fire Magic: 12+4
Energy Storage: 12+1
Fireball
Incendiary Bonds
Immolate
Rodgort's Invocation
Searing Heat
Meteor Shower
Ether Prodigy
Fire Attunement
I don't carry rez sig because that'd be one less doom spell.