Nice work on the guide, although it's indeed full of personal preference, it'd surely help out some people.
Cracked Earth is a really good AoE skill and if you add up all the damage it does quite a bit of damage, and although I really like CE, I don't think it's worth the legacy since a lot of encounters require single target dps, in some cases AoE isn't even allowed. I also think it's good to not totally focus on fire damage since a few encounters have fire immune mobs or mobs with very high fire mits (sammath gul first boss, fornost fire 2nd half of the instance).
Lotrd has a high base damage on it's own, even though it doesn't benefit from the fire damage bonuses, so a +15% boost to that is pretty significant. If you want to stay with AoE damage, I'd rather choose gust of wind (which IS useful for dps, but only for AoE) over cracked earth, since gust of wind does about the same damage as CE non-crit (less for each target, but it affects 6 targets instead of 5), so an increased base for gust of wind would definitely benefit your AoE dps, assuming you actually use that skill. But I rather focus more on single target and burst AoE.