I haven't found a vendor core loss calculator worth trusting so far. Best I've seen IMO is Wurth's REDEXPERT. Overall I've found their calculations reasonable, though I haven't really validated any of them. But for some parts (especially large wirewound inductors) it's easy to determine the core geometry and number of turns, and thus the dB, and putting in realistic material properties gives results similar to their tool. Plus REDEXPERT has a fairly good UI.
As for temperature rise estimates, I never trust those numbers.