When I saw the heading, I thought (to quote a famous meme) "Oh s**t... here we go again". If a ST card/leader/archetype needs to be nerfed, the community just needs to create one thread with 40 posts (20 for and 20 against) and CDPR will wave the nerf wand on ST. For other factions, it needs multiple threads and posts and consistent and constant whining have to be created so that it is slightly touched.
Back to topic: Whatever
@BrokeCiri mentioned makes perfect sense, which is why I think we will never get any new trap, at least not a Gold trap or even if it is a bronze trap, the max it can be will be a dummy trap which adds no points to you either positive for your side or negative/damaging the opponent side. We now have correct amount of traps in which the opponents can think and play around.
1) Don't try to use valuable card if Eldain opens up with a trap - it may be incinerating trap (or even pitfall)
2) If it doesn't open up upon you playing a card, it can be crushing or horn. So, don't row stack, play your card with the row with least number of cards
3) If it doesn't up after two rounds, it is either horn or serpent trap. Now, comes the mind game. Can you assume it is serpent trap and pass when you are < 8 points? Or do you want to get well over 8 wasting your points? Things get tense here and get very interesting.
It is a simple three step logic/thinking the opponent can apply. Accordingly you play around this. But if a new trap is added, then it adds more confusion. If it opens up immediately, it would be duplicate of incinerating or pitfall. If it doesn't at the first turn, the opponent has to play around 4 traps. That is insane.
So, adding any more traps will make it purely unfun for the opponent (if you think about it, pre-HC, we had only three traps, right? Morean who kind of kills the next unit the opponent plays (Incinerating/pitfall). Tourveil who is like the Horn. Morean-Call-Of-Forest who was the serpent trap. If you have anything more, it will just be too much.
Throughout this post I avoided Treant:Mantis as a trap, because it is not. It is neither a trap, nor a unit. It can't synergize with any trap based cards/leader.
But if unitless decks needs to be put in balance, I would recommend nerfing the neutral artifacts. Make Summoning Circle as 12 provision card, and CDPR would have fixed 75% of the unitless decks problem. As I see it Summoning Circle is like portal, even more flexible and advanced and Portal is 13 provisions.
CDPR, if you want to fix unitless non-sense, please fix Summoning Circle and leave my boy Eldain alone.