Do not go top veterancy, they do not depend on that anymore thanks to mastery focusing on defensive buffs. Middle line is preferred now and you'd be surprised at how much they can output on healing as well as resisting ranged. With this they can act as better siege pushers than their other vet line counter parts, however they'll be missing out on bottom's 8 more models. These are only to be used as your final (or first if on attack and if no one else has cheap units for siege engines) unit: to help heal, cleanse and absorb some ranged (or melee damage as a final action) for your team. Always be on the lookout for your teams' blobs and help heal and cleanse negative effects from them. These serfs are not meant to be thrown into the fray anymore; they actually are decent healers. (Throw them in only as a last resort and if you need to buy time for your team to get better units.) (HP doctrines can get them near to 10k hp, their defenses are not worth investing in, just HP)