Need some advice on Borderlands DLCs

HH 1-5 are worth it at a buck each.

Upgrade pack 2 on the other hand depends on would you want to get into the end game grind aka finish game 3 times and then some.(though personally never found much difference between playing on lvl61 and on lvl72(Overpower level 8)

I'm currently playing Borderlands 1 and when I'm done I'm going to be playing part 2. I'm really surprised those 5 weren't included in the GOTY edition. I definitely want to grab them before the sale ends but I'm not sure I'll be able to. I wondering if they are worth it as well.

I'd say the game gets much better at high level play, so yeah go ahead for the upgrade pack. I feel like it's a shame they keep locking extra levels behind dlcs. It doesn't make any sense and just locks some of the best parts of the game behind a paywall.

headhunter dlc is pretty useless, i'd save those $5 and spend them on something else.

This has been one heck of a mixed bag eh?

Ultimate Vault Hunter Upgrade Pack 2 is ok to buy
i think you can buy head hunter 3 because all the head hunter pack is short and only head hunter 3 can help you farm legendary guns easily

The Headhunter challenges are hardly worth, especially if you don't plan into grinding a lot post endgame. They offer some kind of quick boss, a chance to drop some legendaries and nothing else. The UVHU2 is nice, but again if you'll stop playing after finishing the campaign you won't get to reach those extra levels, and you'll need them only on the second new game+ anyway. Get it only if you plan to play a lot more than the main campaign (es. doing raids with friends, new game++, joining other people's games).

If you really enjoy BL2 and want to get the complete gameplay content available, buy it. I loved the game having plugged in over 350 hours so I bought it and I may be a bit biased. IF you not too interested in end game content and raids etc then you can leave it.