In order to target Ansom Parson needs warlords. Problem is, Ansom has the arkenpliers, so he can crush Parson's warlords from the start of the encounter, leaving the Dwagons without command (being a warlord himself he can target the unit of his choice). So even if he tries to attack Ansom's group with a first stack of 5 Dwagons and 3 warlords, he'll either loose all units, or have to retreat after seeing how fast he lost his warlord(s).

Unless he keeps his warlords for the very end, but that will probably proove counter productive in dwagon to elf/gumps ratio.

I'd say that if he's properly informed on the Arkenpliers properties, he'll avoid Ansom. But from the looks of things I don't think he is, so he'll probably learn the hard way and go for plan B (probably the rest of the siege) or maybe even a retreat.