We have the same engine and perhaps circumstances as that Endeavor.
Our engine is 300hp 860lbs torque C8.3L Cummins.
Our rig weighs 31,000+ lbs actual weight and we tow a 5,000 lb Jeep GC.
We have done so for 12+ years and 70,000 miles in the West Coast Mountain Ranges near where we live.
We are never the first, nor are we the last rig at the top of the hill on those mountain grades. We do pass freight trucks on the way up at our 35mph.
The 275 HP can be increased by 50 hp and some torque with a fuel plate and still be ok with the MD3060 Allison transmission.
So, if you are power hungry, in a hurry, type of RVer. Pass on buying the rig.
Otherwise, the engine should not be a obstacle to enjoyment. (I think that Endeavor is lighter than our rig.)