Your choice, but my own view is no. I couldn't get interested in the add-ons. (Different protagonists). The Void Walker Arsenal is definitely a waste of money. I got two of the four packs free with the retail version, and they're typical irrelevant content packs. Anyway, if GOTY goes down to 75% later, the two real DLC will probably go down to 66%, so you'll still get them very cheap, and you won't have wasted money if you find you're not interested.
Oops, missed City Trials. It's basically mini-quests/challenges. If you like that kind of thing, then it's maybe the one thing that would justify it.