Deimos:

Had a 2nd update, additional bits to vaults/etc. 2nd necramech added.

Liches:

Corpus liches added, a few additional Kuva weapons (railjack added as requirement to vanquish).

New solo quests added for story, require railjack and necramech (no need to max out).

The Zariman was added as a new explorable area, arbitrations require completing it.

Random spawn conservation added to Orb Vallis.

Various augment changes, various mod changes, various new arcanes, various new weapons and warframes. MR30 is no longer the max, Legendary ranks were added.

Starter Warframes:

A few buffs, excal had extra slash procs added/etc. No major reworks of most of them, just tweaks to numbers.