If a combat phase has two combat damage steps (because there’s an attacker or blocker with first strike or double strike), Altac Bloodseeker may gain first strike during the first one. If this happens, it will assign combat damage in the second combat damage step along with other creatures that haven’t assigned combat damage during that combat.

If the ability triggers multiple times in a single turn, the power bonuses are cumulative, but the additional instances of first strike and haste are redundant.