As far as the fastest to-kill teams go, the fastest I’ve got is (an admittedly quite popular):
If lucky, Mercy can quickly fill Maw, and Maw can devour the most dangerous enemy troop (usually another Maw). Maw’s Sandstorm yellows help fill IK, and browns help fill Sheggra; IK’s spell creates skulls and reds, which help Maw proc Hunger and fill Sheggra, and Sheggra converts reds into yet more skulls to proc more Hungers and exploit an already-inflated Maw’s physical damage in the absence of Hunger. It’s a very strong team that is only mitigated by a full-Impervious (or Impervious/Stealthy) team.
It routinely kills in under 2 minutes, and can do under 1-minute kills depending on your luck.