Oh! this opens up a can of worms and is one of my favourite hobbyhorses!
First your cache, impossible really to give an opinion before attempting to find, but having looked on the OS map it is less than a km from a road and only a few yards from the old railway track. How that can ever be more than terrain 2 I can’t possibly think. The railway track by definition is flat and you can easily cycle there. The last few yards do not count as far as terrain ratings go, so even a 2 might be high. The nearby caches are all 1.5 or 2. As for difficulty, if no special equipment is needed and it can be found in less than 30 minutes it can’t be more than 2. So a 2/2 would seem fair sitting at my computer, rather than walking around the railway track at Kings Tor 🙂
Generally though, for some reason many cachers want to overrate their caches. Probably because they think it makes a better cache and more people will want to find it. Certainly it helps to fill the grid, but if it’s not genuine then who are you kidding? In my opinion it is difficult to rate any cache on Dartmoor as more than a terrain 4 rating. The following is required for terrain 4 “Experienced outdoor enthusiasts only. (Terrain is probably off-trail. Will have one or more of the following: very heavy overgrowth, very steep elevation (requiring use of hands), or more than a 10 mile hike. May require an overnight stay.)” For terrain 5 it requires the following: Requires specialized equipment and knowledge or experience, (boat, 4WD, rock climbing, SCUBA, etc) or is otherwise extremely difficult.
So which caches on Dartmoor have a genuine terrain 5 rating? The only one I have found all I needed was a pair of wellingtons – hardly specialised equipment. I’ve not done it, but I understand that Satan’s Pit is one of the most difficult on Dartmoor, even that is only rated 4/4. I expect there will be many who disagree with the above, but remember, the ratings only have a range of 1 to 5 and that is to cover every cache on this planet! (plus the one on the space station!)