From the March 2012 Player's Guide:

Walls are blocking terrain for all game purposes except that (a) they are not considered a square of blocking terrain and (b) they are not included in an area of blocking terrain

Element Lad's Transmute special white power

Transmute: At the beginning of your turn as a free action, Element Lad can choose one of the following options: (1) Destroy up to two adjacent objects or squares of blocking terrain; or (2) one at a time remove up to 6 hindering terrain markers, blocking terrain markers, and debris markers (in any combination) 4 or fewer squares from Element Lad to which he has a clear line of fire at the time they are removed; if a debris marker is removed that indicates a wall or area of terrain that was destroyed, it is no longer destroyed.

So Element Lad cannot Transmute a wall into hindering terrain, but he can Transmute a destroyed wall into blocking terrain?

I'd say that is correct. Not many people know that Element Lad is a part time carpenter that enjoys rebuilding walls.

Yep... looks like it.

yes, but the wall will turn back into a wall, not into a square of blocking terrain.

Does this make Element Lad, suck less?

No, actually this makes him worse. Wizkids just nerfed Element Lad.

How did he get nerfed? A wall was never a square of blocking terrain.