You're not seeing the bigger picture here.
Again, the gap being closer to Palpatine isn't implied nor demanded. Likewise for the gap between master and apprentice. It might sound silly to you, but that's the fact of the matter.
The explosion feat is exactly what the description holds: using a Force barrier to resist temperatures at extreme heights. So yes, Cade Skywalker summoning a Force bubble in the center of a massive explosion, and Darth Vader doing that on the regular, is better than Darth Tenebrous handling the mere fireball or remnants of one. The fact they are "two very powerful Force users" is blatantly missing the point. We aren't discussing if Darth Tenebrous is "very powerful" - we're discussing if he's better than Revan, who shits on your "very powerful" individuals with ease.