I can tell you for a fact it did but than someone complained about poison decks and thus the ninja nerf nobody noticed from Sony.
You're right. Poison Elemental should get every single ability in the game, and cost approximately 59 nora. Sounds good to me!
Back in the days, poison elemental used to be able to walk over and trigger its own poison trap. Maybe the adjustment was made to mitigate the synergy.
The adjustment was made to stop Poison Ele from being able to create poison clouds everywhere that it could run and heal through, I'd imagine
Here's the issue -- sand elemental makes sand. So it seems strange for Sand Elemental to hide in itself. The greater issue is that the designers were not sure if they wanted Sand Elemental to absorb sand (Domain Sand) or create sand (Sand Fall and Trail:Sand) and so now he has both and is too expensive. In a similar comment, immunities and eaters are expensive, so it makes sense to have these as upgrades. That way players that don't want to pay for immunity or eater don't have to (they can pick a different upgrade like increased stats), and players that do want immunity or eater can choose that instead.
Sand Elemental is still an elemental made of sand and it's pretty difficult to identify one sand dune to another sand mound. It wouldn't be so strange for Sand Elemental to have Rover: Hidden: Sand imo. For 85 nora, he's also competing with a lot for a slot (see Sand Lord) while having the disadvantage of being a large unit. The only benefit to being a large unit is his bigger Trail: Sand and Sand-Fall but that's only if you Want to use him to Create sand instead of Absorb sand. He doesn't have Tunnel: Sand rank: anything to mitigate the 2x2 roadblock issue either. We could probably decrease his nora cost significantly by making those roles separate since that's what upgrades are for, right? I would suggest removing Domain: Sand and Sand-Fall 1, lowering his nora cost by 10 to compensate - or by 7 if he gets Sand Spray on base to be viable in comparison the other sand sprayers. For Upgrades, change them to Sand-Fall 3, Sand Veil, Domain: Sand and Rover: Hidden: Sand. This way the choice is given to the player rather than an ineffectively designed mix