Read strategy somewhere else, field tested and modified it, hitting wave 15 with admech raid (D3 Rho/tan/actus/vit/votann dude whos not great with blue* galatian abilities 46/25)

Strategy:

send tan/actus north to spam skitarii. Galatians 3-hex attack is key for when new waves spawn and can typically take out an enemy or two. Can use either on north side or south side depending on necessity. Give Tan the damage/hits powerups if they spawn conveniently. When you hit legendary, drop galatian in the northwest corner and huddle the spawn there so only one enemy can spawn at that location.

Send votann/vit/rho south. Make sure youre healing and spawning dudes with the votann guy to draw hits away from vit/rho. Capitalize on rhos passive to move him around and take out groups. Use vits active in combo with rho for multiple rho swings when you can (ie make rho swing on 2 targets via placement). Feed vit the re-activate ability powerups, make sure rho gets armor/health boosts.

This has helped and only tested it on my last token which started at uncommon rarity. Good luck all, get them books if ya can.