so the tier 3 'boss' level
I was doing this with a friend and we got to what was essentially just wheels rolling at us forever
and also zombies
and from what we've seen, there was no way to beat this level. Is there some blatantly obvious way to get past the wave of wheels? Because this is honestly just the biggest 'what' I've come across in forever
wow ok,
we tried attacking them when they were open but I guess attacking it from the front doesn't work or something
oh well

Two tips:
1. Carry totems with you when facing a solid wheel of spiked wheel throw-a-trons. When you put the totem down, it blocks the spiked wheel, acting as a portable shield wall and helping you to advance. (This is especially helpful if, like me, you suffer from lag that prevents effective dodging)
2. There is an issue (possibly a bug) with piercing damage; many piercing weapons are able to penetrate the invulnerable shields, even from the front. The radiant sun shards bomb and antigua series definitely can. If you are on a lower budget, it is possible that the strike needle may do so as well. (ask around before buying one)
There is also an area up top where zombies spawn as you cross the empty area. By using the totem shield wall technique to trigger the spawn, and then running back down, you will have a safe place to hide while far-away zombies are killed effortlessly by the spiked wheels. Don't sacrifice safety to fight an unnecessary battle.

It is basically the game's hardest levels and everything is completely soloable, even the boss. (Unless you lag)
Takes me about 2 hours to do the whole thing.... just need to get used to it, still more fun to run it with a good party though.
Dodge the wheels until you get all the way up to where they're coming from. There is enough space to stand between them if you pay attention and aim yourself carefully. Once you get up to their housing attack it with a sword from beside/behind until it goes poof. Kill them all, and go back to collect the heat/crowns from dead skellies below, then continue forward to the next wave of spiky death wheels :P