I haven't even bothered playing the 2.1 or 2.2 patch content yet.

It's not really tough to 'catch up'.
iLvL 110 is that stuff that's only relevantly harder to get until there's a higher iLvL.
iLvL 70 is now basically an easy wash to equip once you hit 50 and that'll get you into most level 50 content.
For the first coil turn you'll need some LvL 90 stuff but that's not overly complicated.

And then really, if you've got an iLvL70 player you're not exactly 'behind' so much as you're just not doing a couple of the highest level things.
No biggie.