Scarab has HP equal to about 2 Grizzlies, and DPS vs. Heavy Vehicles equal to 5 of them (not counting canister), but costs as much as 6 of them, uses pop equal to 7 of them, and is much more difficult to deploy, given that Tanks are deployed one by one and slowly advanced in tech, whereas you have to wait till tech 3 and 3000 resources are available, then wait another 2-3 minutes before you get the actual Scarab.

So yeah, they are bad.

In comparison, the Vulture has HP equal to 1/2 a Grizzly, but double the DPS vs. Heavy Vehicles, a secondary AA system that is equal to a Volley Wolverine, and their ability, when upgraded, is BETTER than Canister.  It also has flying and superior range,  Sadly, a Vulture still barely wins against even 1 Grizzly, given their solid AA abilities.