Yikes

Returned to the game about 3 days ago to check out TLP severs. Is this abnormal, or should I not even bother?

TBH I did the same, and already started downloading FFxiv, =/ Clearly the money the game is earning isn't being invested into it.

Returning to the game after a long absence as well. Should I move onto something else?

So, for what its worth, I would say no. I would give it some time. If I understand right just had a patch, and well, MMO's have a LOT of code involved in them and **it happens. Give it some more to shake out. This is coming from someone who just downloaded the game and started the tutorial BTW...

Actually I would say this is indeed abnormal. I have not seen anything like this for a long time. As Rolar said, there was a recent patch and those sometimes cause problems. Paaatience, Iago ... patience!

Downtime is one thing but the rollback does not inspire confidence

I came back to the game in October after a years-long absence and I can say with certainty that this is abnormal. Last night there was a 13-hour patch (which in itself was quite unusual; generally 4 hours is the norm). After they brought the servers back up, they started getting crashes, which is what they are down for right now. Most patch cycles go much more smoothly than this. Give it some time before you decide.

This is nothing compared to a normal week on mangler. About a month ago we were getting daily crashes, if not that atleast 4-6 times a week with a up to a 4 hour roll back. I had a PoF c2 group and from a crash, lost about 11 AA from a crash/rollback. GMs dont care and they respond with, "this is why we provide bonus XP days".

So these rollbacks happen frequently?

Tbh the downtime doesn't bug me as much, although it's surprising - it's the rollbacks that bug me, because it's not just keeping me from playing, it's actively negating the time I've spent playing and now going forward I'm just going to have anxiety about whether or not any of the progress I'm making will still be there tomorrow.

Apparently it's the New Normal.

Rollbacks as common as we have had them this week are fairly rare historically, this has been a bit of a bad-patch following moving the servers to new hosting as I understand it, has been a few teething problems as a result.

Also consider that if you have chosen to play on the Mangler TLP that this server was having some serious stability issues long before the latest patch, nightly crashes some weeks & since the patch multiple crashes per day have taken place.

The live servers & the other TLP have been a LOT more stable than Mangler has been.
So if you want the big community Mangler is a great option but if you want stability then right now it definitely is not. Alternative live servers with good US populations are Bristlebane, Xegony or Firiona Vie - note that FV has a special ruleset & you cannot transfer any characters off that server. Antonius Bayle is the Euro Live server.

I play on Phinigel one of the older TLP, unlocked up to TDS currently, which has 2 US Raid Guilds & 1 Euro Raid Guild, small community but friendly & helpful folks there.