My daughters hemangioma never ulcerated luckily, but it is my understanding that vaseline is not a good idea. There are other products used on ulcers that work better, like Aquafor, but hopefully someone with more experience will chime in on that.
Laser is used to help heal ulcers and I know it has good results. Steroids don't help with ulcers, as far as I know, and mainly stop the growth of the hmangioma, although in some cases might also reduce size somewhat. My daughter was on oral steroids for 9 months and her hemangioma shrunk a lot. However she was on very high doses for a long time, which is not usual. I think she was on 4 mg/kg for a few months (started at 3 months old and 6kg at the time so 24 mgs a day) and then a VERY slow weaning process which ended at 12 months old. The side effects can be hard to handle but every child is different and yours might not experience any... In our case her sleeping was a mess, she had high blood pressure, swelling of the body and some tummy problems. She was back to herself about a month after weaning and is now sleeping 10 hs straight (yeahhhh). Good luck and I hope you find all the answers you need!
Marina and Valentina