T1: Kerghit Tariachin because they have ranged weapons. Everything else is utterly useless probably. I guess Sarranid Millets have blunt weapons, might knock things down.
T2: Nord Berserkr because the have 30p throwing axes and decent shields. Hands down the best super low rank IMO. I'd go with these, easy to level them up just hanging onto them for a night or two with training skill.
T3: Rhodok Recluta Balestriere (42p crossbow), or Sarranid Cemaat (Shields + 40p throwing spear)
T4: Nord Bogsveigr (very fast 28p bow), and they're limited @ T4 so they're faster to level than most other T4 options I think.