What are your stats fully buffed ? AC+BM weapon +5 and BM gear fully socketed is more than enough for those instances. You could even get into IS cause you will have the stats required normally. Only instances when maybe you will have issues is sauro 2 keys, SWB, Runadium i guess ? Hyperion only requires 2800 precision and I'm sure the boss in RST/IO is maybe around the same. But even still with that gear you'll normally reach around 2800+ precision and 900+ crit without any buffs even idians and candy. If you try to count for all of that you will easy reach 3000+ precision 1100+ crit. Which is more than enough for majority. (Grendal and Shita requires around 3100, and pashid is 3200 but not really required to have that much for that boss since how the instance works). *and this is not counting having a chanter helping. Having full AC will probably help you more but it's a bit overkill for a class not needing the extra HP and defense (also bonus offensive stats from conditioning is nice), Also takes some time to get fully and that gear fully is almost as good as a full hyperion.
It's just people being very picky, normally some only look at the weapons, some will ask you to show everything, and some don't like seeing "weak parts" even if you reach the stats required. Also some are obsessed with seeing PURPLE. What matters overall is you reaching the requirements stats and being a good DPS. Doesn't matter how you do it. But people don't care, they could be recruiting a guy in full mythical enchanted socketed then he would not know how to play or be a bad person. So just keep trying for other groups or try to get into a legion that runs endgame instances.
For your question about your abyss weapon. Don't waste it under an AC weapon or Hyperion (*you will not loose your hyperion set effect cause the abyss weapon will be fused under it and the latter doesn't have a set effect with your abyss armor). Hyperion base stats are not very good especially for physical classes (magical classes only need MB doesn't matter if it's base or bonus and with full set they get the bonuses and they're good to go. For physical classes from those bonuses the attack is "green" and not "white"). So wait until you get SWB weapon is the best. (RST/IO, Runadium, Sauro are your second option, but you will need to get 6 slots and the best random stats for them to be good).