@NotSoScotia Are you talking about Battlegrounds? Arena system actually picked the highest level in groups. Batte rating is the second priority. When our highest level in group is 44, I never against level 45 pvp gear players. I also got a match up versus all 3 level 45, while we have level 39, 42, and 45 on our side. You may get more winning chance being the highest level with high atk and good AoE skill, or have 3 players with almost exact same level and around the same battle rating. When you are in the same level group, arena system could match you up with "gimp" groups like level 39, 40, 45.
Legendary is always better but it takes whole lot longer to get than arena gears.
The easy way to get lots of inventium is to play the grinder/shredder level multiple times. Do not let yourself to get hurt and try to keep inventium multiplier at 20. You can be lazy and keep jumping without killing the shredder. Plus so people can see.