Best team composition you can think of

No doubt

I post this team because of the horrifying result of facing it in a Grab Bag MotD on Conquest:

Left Lane - Ares (AD/Tank mix) and Kali

Mid - Poseidon

Right - Odin and Zeus

This combination provides horrendous teamfight strength with all having a strong form of AoE, as well as area CC. A perfect teamfight combination would go Ares pull to Odin, Odin Ulti with Zeus dropping ult in the ring, Poseidon Whirlpool on Odin to prevent escapes, Kraken with Kali spinning through the bunched up team.

Even with Purification Beads on every player, they wouldn't be up for every teamfight if the enemy was aggressive. The amount of damage from a good Zeus ult alone + Detonation is absolutely devastating.

In both lanes the poke is incredibly strong, with Kali's scary 2 damage and Zeus's Chain/Detonation. Not to mention when both lanes hit 5 they become infinitely scarier. Odin/Zeus combo is ALMOST a gaurenteed Double (personal experience as Zeus in that combo), and Kali/Ares would have very few runners with Ares's ult giving Kali free reign to tear into the enemy laners.

Poseidon is Poseidon. With great wave clear, poke, and burst.

left: ymir and arachne
mid: anubis
right: hades bakasura/hercules/freya

left was my choice because of experience laning with arachne as ymir. target the squishier person with the arachne ult and ymir ult combo(ymir freezes and walls then ults and arachne uses her web to make sure theres no escape, but if they manage to get out of ymirs ult, she pulls someone for that assurance).
mid was because Anubis is anubis. he has the potential to farm like crazy and kill the enemy mid effortlessly.
right is tricky. Hades is a definate, but bakasura, hercules, and freya can all combo with hades' abilities very well. freya's aoe, or bakasura's ult and 3 with hades ult, or herc ult with hades ult, they all work very well.
the reason odin/zeus isnt in here is because there are the jump escapes that odin's ultimate cant handle. It's an easy escape from odin's ult. While I'm aware that the ult isn't everything, there isn't much of a combo with the other abilities of their's, so if they have a jump, the combo isn't very effective