The Arquitor Bombard is what you get when you cross a Vindicator with Ordnance weapons. And also when you add on sponsons. It is competing against a lot of other entries for heavy support choices in a Legion army, but it can find a role when supporting troop advances and tacking stubborn fortifications.
There is a choice of three main weapons for the Bombard. The Morbus Heavy Bombard is very similar to a vindicator, but with ordnance. It also gets a special shell called the Carcass shell that can flesh bane troops out of the way. This gives flexibility in my mind.
The Graviton-Charge Cannon is a large-scale graviton weapon combined with haywire. This is always going to be good against vehicle heavy enemies and can perform exceptionally well given the right circumstances.
The Spicula Rocket System is a large payload of rockets in two different modes (5 and 7 inch), but comes with the possibility of running out of rockets if the 7 inch mode rolls a 6. I don't see this as a big problem since you will only be firing this (probably) 3 or 4 times in a game and might not choose the 7 inch mode every time. I like the other additional weapons in combination with this one to really whittle down enemy troops.
The cost is steep, and one has to weigh up a vindicator against this slot. The Bombard probably wins in many circumstances, but the trusty vindicator is likely more durable.
Bombard with Morbus. (140 points).
I like the basic version with no upgrades. Take 3 of them if you have the points and the will to use them.
Bombard with Graviton-Charge Cannon. (140 points).
Tempting to take some extra armour and armoured ceramite here to be honest.
Bombard with Spicula Rocket System, Autocannon Sponsons, Havoc Launcher (165 points).
For sheer fire power that might just rival a predator combined with a large pie plate, this is a built that should not be overlooked at all. Take 3 of them to give your opponent a fright. Take 3 units of 3 but beware of not making any friends and your ability to deal with very heavy armour.