Grinding - 4th Sigil Hall

Pardon my potential ignorance here, but like many I'm struggling a great deal with the 4th Sigil Hall. After countless of hours grinding prior to arriving here, I'm still significantly under-leveled. I am moderately patient to the point that 25-35% of my 55 in game hours is just grinding time, but I have no clue where to grind for level 90+ pokemon. It's ridiculously inefficient to battle the YOGSCAST trainers over and over like I've done prior, just curious if there is any particular area good for grinding at all. (Playing on Omicron if its relevent)

Secondly, I'm uncertain if my party is up to the challenge even if properly leveled.

Magmortar, Victini, Zebstrika, Gliscor, Breloom, and Gyarados

I've gone a little out of the way to catch all the dragons from the safari in hopes of them helping, but I'm uncertain of which would help most, as well as ice type pokemon.

I also have considered Regigigas and/or Sableye to basically work as a means to take damage while I heal my other pokemon that would be doing most of the fighting.

Any suggestions could help, thanks for reading!

Yogscast members are the best one AFAIK (although you can grind the previous sigil hall leader for higher lvl pokemon), just make sure you use lucky egg to increase your exp or choice items if you still couldn't OHKO their pokemons with lucky egg.

To add that, ice move won't work on most of Wilson's pokemon, try dragon..

Appreciate that, I saw a little post I don't recall where, where someone had pointed out their "weaknesses" and saw ice on 2 or 3 of them. Anway, thanks much!