Thats all potentially true. The only counter I have, is to suggest you buy as cheap a Litany as you can and try it out on mp10 and let me/us know whether you can tell the difference defensively. I know I can :)
so you would take a ring with:
234 life regen
7% dmg reduction
over a rare ring with:
50 avg dmg
if so then the litany is BIS (to you at least), if you would take the rare then the rare is BIS.
I think most people would take the rare as it would greatly outperform the litany.
This of course is based on perfect rolls (I am not positive the perfect dex/vit roll or max average damage). End Game to me means as perfect and high quality as possible, with the fewest wasted stats that maximized your damage and EHP (self made definition just now). If you arent basing your END game criteria on perfect stats then you might as well call it "Budget End Game" or something similar.
by this definition, the litany is flawed as I said before because:
-70 All res is 10 short of perfect
-4.5 crit is 1.5 short of perfect
-Life regen isnt a top preferred stat by most players
-it doesnt maximize DPS or EHP, which a rare with perfect rolls does a better job at.
Comparing a perfect rare to a perfect litany in my d3up profile (I know results will vary depending on personal gear) a perfect rare adds 22k+ dps and some 15k EHP vs all compared to the Litany's EHP vs elites (50k more EHP to everything else).
Those numbers kind of speak for themselves... I dont think you can keep the Litany as the #1 ring....
EDIT: The question should be, if you have a perfect rolled litany ring, is it possible
to get a better ring? the answer is yes; therefore it should not be considered BIS for end game material...