Help me make a rancor raid team

Have you tried a Vader lead empire team? Even without the zeta on Vader's lead it should be able to easily break those 700k dmg in the raid. Furthermore, getting your turnmeter reducers up to max level will help them land their TM reduction (Tarkin etc. only. Vader's lead is unresistable).
Your best characters are trailing by 5 to 10 levels. Even your arena team. Bring them to level 84. Don't waste credits on characters, you don't use anyway.

If trying the Vader lead, then remember to load your team with as much speed as possible for more frequent chances to remove TM. Currently your speed mods are scattered all over the place (I would generally leave my best mods on my arena team, but still move them around to others, if I need them for raids or events).

https://swgoh.gg/u/dxtrinc/mods/?stat1_5=1

https://swgoh.gg/u/dxtrinc/mods/?stat2_5=1

Do this

Or even better if you do this:

I've been working on teebo. Almost 7*. Gonna gear up and start using him. I also have Phasma at 7*.

Maybe

Teebo
Vader
Tarkin
TFP
CLS (should have him in a few weeks)

Maybe?

Either lightning fast with tons of damage or just pile on the TMR.

The team I'm trying to build up is:

zVader
Jyn
Teebo
FOE

For the 5th I'm thinking Chirrut or someone else fast to provide health. Open to suggestions.

I'm also working towards 7* Thrawn eventually. Just Ezra shards and gear to go.

TMR toons X3
Tenacity down toons X1
Speed down toons X1

Don't waste a zeta on Vader if you can do this with not even omegaed toons. Teebo Jyn tarkin tfp and fox will do job nicely.

You can replace Jyn or tarkin with foo, if you are building up FO for bb8.

KRU for tenacity down, then. And Vader can inflict speed down with his AoE. Only 7* I have with speed down otherwise are RG and Phasma.

Already have my FO squad ready for BB8 without FOO so that won't be possible.

Am I to understand that Vader's zeta isn't worth it?

It'll make it easier depending on what toons you have to go with him, basically. It's a toss-up. How long will it take you to farm enough to zeta someone else versus farm the characters needed to do the raid without Zader.

I used Teebo (L) with QGJ, Ewok Scout, Chewbacca and FOO for a while very early on, before CLS was available or Vader had a Zeta leadership. Could easily clear phase 1, other phases weren't as forgiving cause my mods were trash and my characters were only gear 9 but its a decent starter team if you don't have a lot of resources. Just be sure to give your Tm reducers a potency cross and speed arrow mods.

Nowadays its Akbar, BB8, CLS, Thrawn, Han. Auto battle and complete the full raid in about 10 minutes. Same team can dominate phase 3 of HAAT so they are worth investing in if your thinking about long term.