If your cooling system is up to par and the crankcase is full, you should not be having excessive heat issues with any oil.
If you are turbo'd and you are pulling long grades with a load, then the turbo will be pouring extra heat into the oil and there can be issues...
But if that's what you are doing, you need to be into the owners manual looking at the heaviest oil called for, or allowed. YOU are loading the oil with heat by doing what you are doing.
Delo400LE IsoSyn may not be ester based oil, but it will handle a ton of heat all day every day - just ask Cummins, CAT, Detroit, etc. Some of those rigs dragging 80,000 over the Grapevine do it on 110* days and they do not fail engines due to oil ...
There are many mis-statements in Oil 101, like wear comes from no, or restricted flow. Flow is only important to some bearing types. The presence of oil in sufficient quantities is what's important. There are plenty of engines out there running every day that have never seen an oil pump ...