It might be a good idea to post where these roaming packs usually are! Not one Obliteration soldier has ever shown up on my track in Bloody Kithicor so I am uncertain if it's the right mob or area!
These don't really run all that fast. on a chain horse it was pretty easy to cast 2 spells on one and run a distance away and recast as you pick them off one by one.
These can only be found in the roaming packs of 4-5 obliteration mobs. They are all linked, just like the roaming partys in fort mech (and as explained below they have identical rules / lack of rules).
This means though you can snare or root one (or two or four), the moment another mob in the party gets to a specific distance away - all movement reductions on your targeted mob vanish and they get blessed with runspeed8. You will get no wears off message, and the npc will still have your debuffs listed. They will essentially be immune to changes in runspeed from this point until they are killed by somebody. Additionally, because of the many objects in the zone (trees, brush, rocks) if one in this party gets briefly stuck and decides to warp to you - the rest of the party gets runspeed8 and immunity to runspeed changes and may warp to you as well due to their leash distance being tripped.
These targets are only reliable for groups that can handle 4-5 mobs at the same time.