How hard of a duo will a tier 4 genger be?

I’m not sure if they will make them tier four stat, but if it does turn out that way, I’d say it would probably be intermidate to hard depending on the moveset, weather and the team being used.

Pretty hard, especially against Shadow Ball. But not impossible. You will probably need to rejoin though.

You can simulate any raid you want on pokebattler. Even a tier 4 gengar. Check link below.

I would say it’s intermediate: can almost be done 2 players with no friends bonus and easily when best friends. Timing out marginal seems to be on par with houndoom; harder than absol and tyranitar. Easier than marowak.

https://www.pokebattler.com/raids/defenders/GENGAR/levels/RAID_LEVEL_4/attackers/levels/40/strategies/CINEMATIC_ATTACK_WHEN_POSSIBLE/DEFENSE_RANDOM_MC?sort=ESTIMATOR&weatherCondition=NO_WEATHER&dodgeStrategy=DODGE_REACTION_TIME&aggregation=AVERAGE&randomAssistants=-1

Edit:

checked pokebattler a little more.

IMO:
Gengar has A LOT of attack, the only pokemon that is bulky enough not to make you time out is tyranitar (excluding gengar has Focus blast). Even so you will need 6 tyranitars as lvl 40 not to time out duoing it.

It lacks in defense. They key is really beeing a DPS junkie, if you have 12 good counters and can switch in the looby quickly timing out doesn't seem to be a problem.

Confusion is they key in many cases. Giving a extra 5-10% more DPS. In particular with Espeon and Zam. Guessing not getting that many charge moves fired means single bar charge move gets more dependent of the quick move.

probably too hard

Short answer: Middle earth between Absol and Tyranitar Duo Raids.
Long answer: When you look to Gengar average raid boss stats, it has high attack (201) and really poor defense (124). The thing with Gengar is that hits like a truck and it has very hard-hitting moves. All depends on the moveset. If it has Focus Blast, you only have to use Mewtwo and other Gengar. If it has Shadow Ball or Sludge Bomb, then Tyranitar will be your best bet. Not a hard duo actually.