Being an owner & user of the 15" MacBook Pro forever; Over the years the 15" has frequently struggled with it`s thermals, especially when an external display is connected as the dGPU switches on as default, internal temperatures soar;
- Elevate the rear, aluminium passive coolers generally work best (I use RainDesign`s mStand & iLap)
- Increase base fan RPM to 3K or as much as you are comfortable with (MacsFanControl or SMC Fan Control)
- Limit the dGPU`s usage with gfxCardStatus
- Swap out Chrome for Chrome Canary as it`s way more optimised for OS X and will extend battery run time, reduce thermals
- Swap out VLC for Movist as again it`s a reduced load on CPU/GPU
- Uninstall or block Flash
- Install an ad blocker Ublock extension works well
- Powered coolers are very much a "mixed bag" when it comes to Mac portables, you need one that has a high capacity (100 CFM minimum) and preferably a large single fan, this can help to keep the 15" internal fans below 4K which for many is good enough as often it`s this point and beyond where the fans become intrusive. Don't expect a powered cooler impact internal temperatures, beyond a couple of degrees
- Older machines can benefit from cleaning the cooling system
- Replacing the thermal paste has been hit & miss, some with very positive results, some with no improvement over stock. Personally I would only do this on a Mac Portable that was either very old, or one that I can confirm was definitely running hotter than stock.
- If your MBP has a discrete GPU, it will fire up when an external display is connected as default, temperatures will rise rapidly.
The key to a quiet life with a 15" MacBook Pro is several incremental changes that do add up to reduce thermals. From my experience over the years if your going to push a 15" hard the fans are going to max out fast, with associated noise. If your using it with a moderate load life can be made quieter

For the most part your MBP runs hot as that`s how Apple designed it, the trade of for form over, function, thin & light...
Gaming is always going to push a Mac portable to it`s limits, equally "if" you can reduce the temperature a little, it may just allow for a much better in game experience. As everything adds up, close all App`s pro to launching the game, it`s all about small gains, not big wins.
The old adage still applies; it`s easier to keep a system cool, than cool-down an already hot machine. This being said it`s not strictly necessary, equally it`s nice to know that there are options for reducing temperature out there.
For the OP ambient temperature is fairly high, at 30-35C, if you can reduce it, this too will help your Mac. Bottom line is only way you are going to play these types of games is to reduce the system temperature. Given circumstance you may want to consider a cheap gaming PC, and a Smaller Mac. Cost wise it may well work out the same.
Q-6