STA does not affect regen. Regen is fixed values per tick, not % based. More STA increases your hp pool, by 5.3/point at L60. So dumping all your points into sta will give you an extra 106hp at level 60 and far less than that at level 1. It is more difficult to max than other melee stats, but perhaps less so than int. If primarily grouping, more STA means more efficient heals for clerics L39+.
More INT means you will last longer without mana regen. Large mana pools are generally overrated because it all comes back at the same speed. However, tiny mana pools can be a detriment in longer fights without mana regen.
Getting AGI to 75 is a must. Getting it to 85 so you can still be at 75 while wearing a fungi is a worthy consideration, but a fungi is not just around the corner for you either ^^
|