It's an interesting topic, im suprised they have stuck with the Taz/Tenay team for so long considering how little chemistry they have. The best period for TNA commentary for me was the brief period when they had Don West turn heel, it was entertaining and had real promise but they dropped West from commentary the moment Taz became available. A move they made because of his 'big time' WWE connection and not for his talent on commentary in my opinion.
Taz is likeable enough but very rarely says anything interesting or funny, Tenay hasn't got the voice for play by play, horribly shrill and grating imo, but i thought he was perfect as the '3rd man' on commentary in WCW, offering knowledgeable insights. The question is do Tenay/Taz add anything to the product and the answer is an emphatic no.
Hell id bring back Shiavone, in my opinion one of the most underrated commentators out there, i always preffered him to JR. He has a great sportscasters voice and is one of the best at hyping the big and small events and storylines.
One thing i always find oddly funny is when Tenay and Taz are on camera together, when one is talking the other will pout, if u haven't noticed it watch out for it!