During the closed beta period when MCC's were vulnerable it was never an issue. In fact this was all the way back during skirmish 1.0 from what I recall and the reason tanks were spammed was due to a few other factors. First and foremost...

1. Tanks were free during this period. As were dropships. Both were spammed equally, as small turrets had incredible splash and ridiculous range. Dropships at the time also had no damage from collision, so they were used to smash into people on the ground in a highly trolly manner. Swarms couldnt really do much, so it was a case of either get in a tank and avoid being dropship crushed/spammed from towers, or get in a dropship yourself.

You may remember that one week earlier in the year when payout was bugged and people were making millions in every match. People would use all kinds of expensive stuff during that period, and that just proves people will go HAM with stuff if there are no consequences.

2. Defense relays/installations had to be busted in order to win. You did this with tanks. It was a necessary part of the gameplay at the time, so you couldnt really avoid it.