I *love* using Chi Chi and the free swap is genius, I didn't think of that
Probably because I'm needing/liking the extra damage from the Rot+Undead+Stampede thing.
I like the Rot part of the combo a lot as well, but you can also use a pet like the infected squirrel and do:
Chi-Chi: wild magic
Inf Squ: Creeping Fungus
Inf Squ: Stampede
Bling (make it rain + inflation) and blighted squirrel (wood chipper + stampede) have similar setups. Macabre Marionette has a couple of good combos with Dead Man's party as well.
With setups like these, the extra DoT makes up for the Rot damage if you are against an enemy where the DoT is strong against them. As an example, on Taran Zhu, the combo I mentioned above has creeping Fungus ticking for near 500 damage per tick, which obliterates the first Humanoid, even after he feigns and chips away at the second one enough for a good sweeper to finish.
Rot however is a much more versatile way to go if you don't have a good DoT that is strong versus your target. Ironically, I used the Rot,Wild magic, stampede combo against Chi-Chi using the senjin fetish and a giant sewer rat.