Enhance is already great. But work is never truly done.
I can suggest a few things that you could do even now.
1: Windfury totem just a standard raid buff, this is the only major problem i have at the moment with enhance. I really DO NOT like windfury totem, especially as a spec talent.
2: Chain lightning hits 6 targets. Everything is capped or soft capped at 6, aside chain.
3: Crash lightning buff from chain lasts throughout the whole duration, instead of just the first hit.