I've played quite a few Mentor matches, on different maps, and my general experience is that enemies in these Mentor matches are a lot tougher than the difficulty on the results screen would indicate.
For example, I played a 77% difficulty non-Mentor match on Weapon from the Past. Regular Wardog enemies needed two 80 damage Strikes to take down, and their melee damage was about 25. The Wardog Captains' incendiary pistols would hit me for about 25 damage, as Konstantin.
I then played a 45% difficulty Mentor match on Hanging by a Thread, and enemy health and damage was pretty much the same as I experienced at around 75% difficulty. Bear in mind, that these are matches with low level players that don't have the same passives or weapon upgrades, so they're going to have a very hard time, and a poor first experience.
I remember watching some of the low level players try to take down a Hades Brute in the last section, and it seemed like it would take them 10+ Strikes to take one down. Regular enemies would also be a big threat to newer players, due to their high health and damage.
These matches usually just end up with the newer players dying a whole lot to regular enemies and Elites alike, and oftentimes just disconnecting and never coming back.
On the other hand, I've played non-Mentor matches at the 40-50% range that were significantly easier than the Mentor ones, as enemies didn't hit as hard and had less health.
This problem should be fixed soon. For veteran players it's just giving them an extra headache having to carry newer players through maps, and first time players are going to be wondering why this game is so hard.
I'd suggest just capping the difficulty of Mentor matches to a low level, around 20-25% difficulty, regardless of the average MMR of the Raider team. My MMR is around 85% right now, and so my presence is usually going to skew the difficulty quite a bit.
