Melee Warmages are mainly concerned about strength. They need all the AS they can get relative to the other classes before the AS slowdown. AgiDex is less of a concern because, from an RT perspective if you are doing most melee builds, you should be able to swing anything in 6 seconds with any race. That is the RT needed to hit 1 second eventually. If your stats are placed for growth, and you are using a lance, AgiDex might be a concern in a few cases. In that case just make sure you math it out before you get started, or swap to a faster polearm.
The strongest races are:
Giantman: +15 STR, but bolting suffers with a -5 DEX and CS takes a hit with a -5 Aura. They do have a nice CON bonus at +10 and the best encumbrance factor of all races.
Half-Krol: +10 STR, with no bonus or penalty on DEX or AURA. They share the same +10 CON bonus as Giantmen, as well as a high encumbrance factor.
Dwarf: +10 STR, no DEX penalties but -5 to AGI and bad Aura at -10. They have the highest CON bonus at +15.
Human: Only +5 STR, no modifiers to DEX, AGI or AURA. Humans are the middle of the road race.
It should be noted that these THW warmages races outlined above tend to be weak in DEX and Aura if you decide to swap builds after the AS slowdown. So you would find it very difficult to swap from a Racially maximized THW Warmage to a Pure or Ranged Warmage.