I always monitor:
Regen Rate
Recovery Rate
ToHit Chance
Damage Buff
Recharge Time
Depending on build (res vs def, for example):
1 paired resistance (S/L F/C, etc.)
Melee def
Ranged def
AOE def
1 other paired resistance
For typed defense characters I monitor one paired defense (s/l, etc) of each pair and a resistance to see if I've been debuffed. For resistance characters I monitor one from each pair and then one of the vector defenses for similar reasons.