Btw @Dice_nick20, which champs do you main?
Show your roster. Ragnaruk's information on the bosses is correct. You will 100% need unstoppable counters and bleed champions, as there are a lot of those paths in later acts. My MVPs for act 8 were Mr. Sinister, Kate Bishop, Onslaught, Hulk, and Juggs.
Ok this is from the top of my head, guys please correct me if I’m wrong. Herc destroys the 81 boss easily. Shang chi kingpin zemo and Cheelith( purify/cleanse- has to be instant, so not Nick) for 82. Any cosmic with unique buffs especially Odin galan and venom destroy 83. For 84 any mutant with high special dmage destroys. For 91 it’s about damaging debuffs excepting bleed, so iron heart and lady d are great. Overall, however, champs with good utility. This may sound generic but you will really understand what I mean once you are venturing into the later acts. From my memory a good unstoppable counter is necessary for the later acts so bill, Cheelith and Shang are excellent. Miss/ falter is a problem as well, so onslaught prowler and bullseye are awesome. Auto block isn’t really from my memory, but a Vox would never hurt anyone. Evade, as well, so I’m thinking the likes of prowler Kate and professor x. Also many later acts have a node that reduces true effects by 100 percent so it’s best to have champs who CANNOT be evaded or have access to coldsnap, so professor x, prowler Kate and even aarkus will be invaluable later on. Immunities as well is great. Quite a few bleed/ incinerate risks from my memory so champs like colossus and nefaria, especially nefaria will be invaluable. ESPECIALLY nefaria or some power gain control menace such as Chavez will mean a lot, as I remember there was some node where they gained power a LOT so using nefaria was like having power back boosts. Despite EXTREMELY popular option, doom is in fact very very useful for the later acts, yet more for act 8, as some nodes in act 9 punish mystics from my memory. Also prioritise champs who can deal with dmage such as regen champs like toad or the ultimate debuff punisher, in the form of sinister. Mags will also get you quite far on his own. Champs with extremely high special dmage will save you from a lot, and the best champ for that is obviously professor x. Sorry, a decent amount of this mentions champs I used in the past and like, so I must clarify that the one I hate SILK will help you a huge amount. Hulk’s stun lock will get you out of a lot as well, a decent amount of science champs really and truly will be just excellent for your run. Crossbones could handle the majority as well honestly, but you’ll probably be fine with your current roster. After act 7 your roster should be versatile so honestly, just reading the nodes properly will save you lots of revives, opposed to not having the correct champion.
MCOC Noob will tell you which kind of champs are best for each quest, I highly recommend his channel. Rank up that Sinister as much as you can, he is insane. Even is he is not recommended on the path, he will probably work. He carried me through act 7, 8, and 9. In response to your Chee'ilth question, yes you should rank her up. Her bleed damage will get you through a lot of paths.