Why would anyone ever take a Bombard?
The Basilisk has reach and punch.
The Hydra has AA and punch.
The Manticore has reach and lots o'punch.
Code Sample:
Basilisk  AV 20cm 5+ 6+ 5+
Earthshaker   120cm  AP4+/AT4+ or 1BP, Indirect
Heavy Bolter    30cm  AP5+
Bombard  AV 20cm 6+ 6+ 5+
Siege Mortar   45cm  2BP, Ignore Cover, Indirect, Slow
Heavy Bolter   30cm  AP5+
Hydra   AV 30cm 6+ 6+ 5+
2x Hydra     45cm  AP4+/AT5+/AA5+
Heavy Bolter   30cm  AP5+
Manticore AV 20cm 6+ 6+ 5+
Rocket Launcher 150cm  2BP, Disrupt, Indirect, Slow
Heavy Bolter   30cm  AP5+
Barrage  Extra  Extra Blast  AP AT
Points  Templates  Markers
 1    None    None   6+ 6+
 2    None    None   5+ 6+
 3    None    None   4+ 5+
 4-5   One     None   4+ 5+
 6-7   One     One    4+ 5+
If it has Walker it could be useful for close support for Catachans, or Move 15cm and thus Garrison, but that's about it.
