Well, I never tried that with them…Funny story 
I also never knew about the difficulty snapshot as you explained it, but that would be most useful on starting a new Season going for the Cube. Playing hard-core, and being at around level 6–8 when I get to the Elder Sanctum, those Elite Rat Kings have sometimes cornered me and killed me. Being able to snapshot those to a lower level would be very useful.
About this leveling problem, I encountered it on Season 28, and now, and only using the all items set to level 1 function of the Altar. And I know it’s happening because I walk into a level, kill 4 monsters I’m at level 6. after that, each monster I kill provides less than 1% of the XP required for the next level. If I abandon that level and run to the next, I get the same thing entering it. Six monsters And I’m at level 14 and then every monster after that, a tiny fraction of the bar. It’s real, it’s happening, and it only happens with this gear.
I just ranked a Gem of Ease to 25, and I’m going to take off all that level 1 gear, put on the level 21 Born’s set, in the level 23 Cain’s set, put that GOE in my weapon and see what happens. I’m pretty sure it’ll be back to normal, but it’ll be difficult to make any comparison because the XP provided by the GOE makes a lot of difference.
I know I can use the level 70 versions of these sets, but I think that would bring along the same problem I’m already experiencing. I really get stitched up about all this, I’ll level up two new characters, one using the low-level sets, and one using the level removed 70 sets. All other things being equal, that might be an interesting experiment.
At the time of this writing, 8:02 PM, I’m at level 29.
8:05 Level 55.
8:08 Level 59.
Okay so now I put on the level 70 versions of Cain’s, Born’s, Capt. Crimson’s, Guardian’s, and I still have the Hellfire ring and amulet and Leoric’s Signet. I have the GOE in the weapon, and a Fragment of Destruction in the helm. Have rank 80 Banes of the Trapped and Stricken, and a rank15 the Bane of the Powerful.
8:31 PM, level 59.
Got a network disconnect…again…no death.
8:53, Level 66.
8:56 Level 70.
What does this show? Who knows, but it’s been interesting tracking it…