Tahu gained Rahkshi powers after absorbing their Antidermis during the Battle of Bara Magna, but exactly which powers he gained was never specified. Did he gain all 42 powers? If not, can we get a list of which powers he attained? We are only aware of two right now: Heat vision and Quick Healing.
If I recall correctly, it was stated somewhere that the Rahkshi army in Journey’s End contained all 42 variations, and that they were all depicted as all Heat Vision in the comics in order to help sell the set.
So yeah, on top of what he already had before he obtained the Golden Armor, he now possesses all Rahkshi powers from the prime Bionicle universe, regardless of whether or not he was shown to have them. And, as stated in a compilation topic of Ask Greg Answers over on BZPower, this also makes him more powerful than Tuyet and her Nui Stone.