2 Jaina's applying and capitalizing on chill and the damage buffs therein is beautiful... not to mention the insane cc that is going on... Jaina simply synergizes quite well with Abathur's Ultimate Evolution (Hero Clone ult)... albeit how Jaina specs matters somewhat.

Lingering and Deep Chill at level 1 are a tossup.

Frostbitten and Ice Flows are a tossup at level 7.

Level 13 - Storm Front (The increased range) is very important simply because Aba's clone has limited time thus does not have time to position the ideal Storm Front... especially since when smart teams see the Aba clone coming, they simply try to run to wait it out.

Depending on your team, Norther Exposure might make more sense at level 16.

The Cd and increased spread at level 16 is quite useful for the Aba clone... for cd's are everything...


Abathur Build (warning, wall of text and ramblings):
http://www.heroesfire.com/hots/guide/abathermite-wall-of-text-w-ramblings-clone-locust-strategy-5261