Ninja of course is an amazing damage dealer, but MAKE SURE to read the guidance below as he can easily mess up this team depending on skill priority and affinity.  As always check first in the calculator!

Helicath will block the damage for the AOE’s and use his shield to keep your stun target alive.  To maximize the shield ability, you will want increase defense before that skill is used (any champion but the 191 champion) as well as low HP (and/or high defense) on your stun target.

253-254 – Helicath
186 – Doompriest or alternate cleanser or DPS if using Debuff Blocker
175-177 – DPS.  Must be faster than Ninja.
172.75-174 – Ninja. Must be faster than slowest champion.
171.75-173.00 (slowest) – 3 turn debuff blocker or DPS if using a Cleanser. Must be slower than Ninja

The 186 will always go first after AOE2 to cleanse debuffs and/or to cleanse the Stun. Doompriest can cleanse both and as such is an ideal fit to make this affinity friendly.
If you’re using Block Debuff Champion on a 3 turn cooldown (Underpriest Brogni/Grizz Jarl/Tatura Rimehide) instead of Doompriest, then you want to replace the 186 Doompriest with a 186 DPS and the slowest DPS champs with a block debuff champion.
Hellcat’s A2 and A3 needs to be fully booked out to a 4-turn cooldown

Hellcat can run full auto from the start (read below for how to run Ninja); Begin with his A3 then A2 on UNM and on NM start with his A1, then A3 and A2
These can be set in the skill prioritization to run full auto.

Ninja Rules

Ninja MUST CRIT on his first A1 on UNM and BOTH of his first two A1 attacks on Nightmare.  If he does that successfully he can be used against weak affinity.
I believe with the following setup he can be used. Prioritize his A3 over his A2 skill.

For UNM: A3, A2, A1, Auto (this can be preset to run full auto from the start – just confirm the crit on his A1)
For NM: A1, A1, A3, A2, Auto (you will have to manual his first two attacks then you can run Auto after that.  Those first two attacks MUST crit.)

Stun Adjustments

You’ll want to avoid the stun going to anyone who will drop the shield from Helicath.  Generally this will mean avoiding your Block Debuff champion.

You will need a block debuff champion with a 3 turn cooldown on that skill.  If you want to block the stun debuff as well, a 2 turn duration is required, otherwise you’ll want to avoid the stun hitting both Helicath and your Block Debuff champion.

When using a cleanser, Helicath won’t be cleansed from the stun on Nightmare difficulty – avoid him getting hit.