Iotss is very easy. Just use boneyard offscreen. If you don't know the map layout, use the map reveal and you'll be able to see that there are very narrow paths that the enemies can walk down, so aim your boneyards down the path ahead of you and it'll be easier. For Malic, all you need to do is keep summoning minions ahead of you offscreen until you can see that the missiles aren't targeting you anymore. Once that happens, you can move forward (don't need to use teleport if you don't want to) and let your army swarm. Then, you can just casually hang back and spam funeral pyre til he dies.
Lucion is a bit trickier since he can "float". Make sure you kill him on a walkable area and not over the water or else he won't drop his items/charm. If you get closer and see that he is fire immune, then aim your boneyard at an enemy right next to him (the enemies are invulnerable while he is alive, so hit them with the boneyard and let the nova explosion damage Lucion). Your other easier option is to slowly lure more enemies up and right away from Lucion to help reduce the density of the attacks while they're invulnerable. Just lure them out of the shield range and pick them off as needed.
Bremmtown (didn't get a video, I apologize), do not use your totems. You don't need to and you won't teleport here so there's no reason to have them. Summon any minion ahead of you around the edge of the screen, step up enough to trigger the spirits to pounce onto your minion, then funeral pyre til that packs dies. The width on FP is enough to cover the pack, so it should go quick. Repeat that all the way down left and then down right.
When you get near the bottom where the dragon is, hug the upper wall. Sometimes he will shoot a death spiral before you see him and before he comes around the corner, so it can reach at an angle up the path, but hugging the wall will allow you to stay safe. Once you can see the corner bend, summon some minions there, wait til he's visible and blast him with FP. TP to town and cube with the arcane Crystal.
Note that even if you kill the dragon outside of three minutes, you'll still get swirls, so if you find that you have swirls but the cube recipe doesn't work, you were just too slow. Before entering, it's not necessary, but if you want, type in /time 185
That command will set a timer in blue text in the game for 3 minutes and 5 seconds (uses the number in seconds for the command). That gives you five seconds to enter and begin, then three minutes to get the dragon killed. You'll only see the timer notification again when the timer expires, so as long as you kill the dragon and get swirls before you see that notification, you're good to go for cubing.