They take 5 sec of standing idle for the added vision to kick in. This is too painful to use for scouting, not to mention that it can get counter-spotted by the dingo and get shotted at by atgun in midgame without a way to scout without getting damaged. 

I will gladly throw away the combined arm aura if it let me have a unit that actually fulfils its role like before . Anyone who didn't value the importance of reconnaissance and counter-intelligence is playing with deficiency and that's their own faults, why cater to them to destroy a fundamental aspect of a faction? Lower dps? Fine, lower health? Fine, but don't destroy basic features of rts as a whole

I prefer the CA over the better vision. The bonusses for your Panzergrens just help you so much in getting a good foothold in the early game.

For mid/lategame scouting, we now have the buffed recon tractor in T2. That thing can scan a whole 1v1 map if you park it in the center. It's pretty crazy.