The point of a wall segment is to direct movement AND block shots. Tanks will not be able to shoot over walls as far as I know. Also yeah, once Artillery gets a spitshine tankblobbing should become less popular. It will also see a decline when diverse tactics get a bit more focus, I.E. synergy between orbital and land, surgical strikes, transport flanks, naval support, etc. etc.
The real problem its that scout in early game its not so fluid. You have to keep rotating the planet orbit to scout enemy and rotait again to see what you´r doing,might become confuse to many players. But iff you got enemy next to you ,obvius its easy. In long game this will become a problem indeed,doing many tasks and at same time and keep rotating planet ,not many will enjoy ,but its like it is!