That cloud tileset has been breaking physics a lot- the south cloud edges in particular, since they're set to passable so you can walk in front of them. I'll have to go through the Aerialite Caverns again and make sure physics aren't being broken there either. Probably will have a patch out late tonight.
As for Star Burst- I compared your saved, more defensive gear set (with Pure Shield+Spellsteel Robe) with the same gear set, but with the Battle Shield and Sage's Cloak replacing the Pure Shield and Spellsteel Robe, both from the immediate point you saved at and both on the same Hollow Howler with 6 Starforce.
The Pure Shield + Spellsteel Robe set did 77 with the 6-point Star Burst while the Battle Shield + Sage's Cloak did 93. As expected, the damage increased by 16, equal to the increased attack of 8 multiplied by 2 because of the Cursed Coronet. It seems to be working as intended. Did you have a lot of Starforce built up when you used Star Burst with the Pure Shield and Spellsteel Robe?