Had DURO bias they all slipped belts just before 3 years. Then went Denman "D" rated and they lasted about 3 more years, two slipped belts, one lost the entire tread. Then put on MAXXIS 205/75R15-D and they seem to be holding up well. Yes I run mine through the desert periodically at 115°+.
Only 14" I know with more capacity is Kumho 857 at 2271 pounds 65 psi.
http://www.tirerack.com/tires/tires.jsp?tireMake=Kumho&tireModel=Radial+857Otherwise you might need to go 15"+ wheels.
With new tires (check the date code) I would run them as is one season and get tires upgraded next year.
When you upgrade make sure the tires are rated for the full trailer GVWR. JMHO.