The problem is that devil raid bosses have evasion on higher difficulties, and still have a decent reflex save on normal as well, which leaves eladar's electric surge (an shocking grasp) as the only non-evadable source of dps an efficient damage.
Even with resistances, spamming no save spells like polar ray and frost lance SLAs, in addition to niacs biting cold is almost always higher dps then spamming ball lightning, lightning bolt, or the horribly slow casting chain lightning.
Now that acid spells stack, earth savants cant do much more efficient damage as well, but might not be quite as much dps.
When you look at non-devil raid bosses as well, some of which are immune to lightning, the other savants have a much larger lead over air.