DLC 3 hands down has the most interesting story concept going for it! There are new additions of monsters along with two new rogue servants which are both VERY fun to play. It feels like the type of story you'd find in an event for Fate/Grand Order. Compared to DLC 2 there's for sure more bang for your buck here. I also love that Yui got more screen time, super cool to practically have her take center stage seeing as she is my second favorite master in the game.
Overall, I recommend it. There is definitely less filler and more substance here compared to DLC 2. I still think all of the DLC could be cheaper but I like to support Fate games. Maybe wait for a sale and don't pay full price. Also we should have gotten baby Iori!!!