Ether wrote: So how can the russ make up for these deficiencies?
By being more reliable as damage dealers. Basilisk can easily miss it's target with unlucky roll of the scatter dice, especially if you are shooting from behind the
LOS-block, but when you make 20 to-hit rolls for Punisher cannon you can be pretty sure that you'll get about 10 (with BS3) hits. And remember that:
a) tanks can tank-shock and ram;
b) some of them have AV11 rear that make them immune to small arms fire;
c) they can shoot flyers,
FMCs and "invisible" units that is impossible with blast weapons;
d) they can inflict multiple wounds at monsters and other T5+/Eternal Warrior models, while Earthshaker is limited to 1 wound at best.
Of course, artillery has it's own advantages you have mentioned in your post but it is more of a complementary to tanks than their competitor.