Ascended armor?
The bulk of the power in full ascended comes from the weapons. Armor is a 5% stat bonus. If you’re wiping, it’s not because you don’t have ascended armor.
The only point at which ascended armor becomes mandatory is for Tier 4 fractals due to agony resistance.
Ascended armor is really not needed for raid. The difference in dps is very small and so is the added armor. That said, in pugs people don’t know you so not having ascended armor can be a red flag for some. Not that the small decrease in stats will worry them, but they will asked themselves, is it a character that he mastered if he doesn’t have an ascended armor? Do he do fractal and dungeon if he doesn’t have an ascended armor or do he just open world? Did he just start doing raid if he doesn’t have ascended armor? So if they have to choose between someone with or without ascended, they will usually choose the guy with ascended.
So my advice is to gear up the character that you would want to play the most and slowly gather what you need to gear your second character. If the raid you are in need a revenant, then use your exotic armor rev (as long as he have ascended weapons and trinkets), but just be aware that some group (not all) might kick or ask you to change to another character with ascended.