Hey there, we have the exact same gaming resume pretty much in terms of MMOs and TES except I started with Meridian59 (so I am more leet than you by 1 year, LOL J/K).
ESO is primarily theme park with a few sandbox elements IMO. About 85-90% Theme Park. Its PvP is zoned but the zone is large and seamless and there are PvE activities there such as questing and open dungeons. It utilizes DAOC 3-faction AvA.
There is plenty to love about ESO, most of which I can't talk about due to NDA. The real beauty of the game is in its details.
Crafting is not great but not terrible. It's no SWG crafting but it's not as simple as WoW's or GW2's and it will be vital to end-game.
The combat is great. Could it be better? More like TES? Yes, but just having first-person with hands and having to sorta aim to hit is good enough for me right now. Definitely a refreshing change from most BS mmorpg combat systems.
You will not NEED a group for most things. In fact much of the main story is solo-only (something I find terrible - solo-able is fine by me but I should always have the option to play with my friends through everything if I want).
You will need a group for end-game PvE adventure and progression dungeons, and lone-wolfing in PvP will be nigh-on-impossible unless you are stealth-ganking lone questers.
Sadly the game is highly instanced and highly phased, making group questing a serious PITA. That being said there are no loading screens between zones a la GW2, but there are slight loading screens on interiors, some dungeons and the like, very, very fast.
Can't really say much more than that I don't think.
Also, have not played either Final Fantasy MMO as I always disliked the franchise so I cannot speak on its potential similarity to either.