There was a post on this forum with details stats showing they were better value than farming mods from the challenges, mostly due to the fact you get higher quality ones (no whites), and more importantly, an equal distribution of all slots (as many Arrows as Squares). Farming good mods from the challenges is just not an option.
But after saying why mod packs are good, it's sad to say that since there's no tournament on the agenda anymore and they seem to pop up with tournaments, nobody knows if/when they might come back.