Taken about 2 years but finally got all badges. Grandmaster score chaser was the hardest one for me. Had to complete with 7 challenges to get it. Doom slayer was tough too but when I got the right build I absolutely smashed yog for it.
Yeah I only had badder bosses on for that one. And you're right, not easy with the extra mobs. I use a warden build and managed to get a good RoW run, loads of healing pots and a ring of furor+8 with a glaive, wand of regrowth with camouflage to keep away from everything.
You have to use everything to your advantage. Seeds, stones, scrolls, the environment, everything. Circle around pillars or grass, and you'll land surprise hits, which guarantee a blow every time. Funnel enemies through doorways, don't get surrounded.
Any floor that has a puzzle room, such as needing to float to reach a chest or a room full of gas... that floor also has the exact Potion required to solve it.
Flies sometimes drop a potion. It will always be a healing one. Same for bats later on. Dew drops heal you.
You have to learn from every death, learn what every item can do. You will get there!
I'm still learning. The guys cruising a 9 challenge run still blow my mind.