A couple of thoughts - some of which many of you may agree with, other thoughts many of you may not.
First, what makes up a great rivalry? Many components, but generally great hard fought games, players who dislike each other, coaches who dislike each other, and fan bases who dislike each other.
- Dee certainly had no love for anything orange. Both teams wanted to beat the tar out of the other team, and I suspect no love lost there (anyone else remember "Boo Randall"?).
- Pat accused Geno several times of cheating, and he had no tolerance for that since he did nothing wrong. No love lost there. Add to that - she hated his Philly sarcasm, and he loved to tweak and irritate her Southern facade.
- Even now the fan bases dislike each other, and for the most part, dislike the other team.
- Most games back in the day were between 2 top 5 teams, often #'s 1 and 2 so they almost always had big implications for the national WCBB landscape
However, even towards the end of her career, Tennessee was falling off. The game had passed Pat by. She was trying to update offensive schemes, famously by canoodling with Harry Paretta to learn motion offense, but still, the Tenn mantra was "get kids with great athleticism, tenacious defense, stale offense, and score off offensive boards and putbacks".
The thing about that strategy is that Pat was WAY more charismatic than Holly and was able to demand and get more out of her players so her teams performed better. After Parker left with the 2 NC's, Pat coached 4 more years, had a total of 26 losses, and the NCAA appearances ended in exits in the 1st round, sweet 16 and a pair of elite 8's. Honestly, no better than Holly has done since then (3 elite 8's, 2 sweet 16's, 2 2nd round).
Pat was a legend, but her team was already falling off and while it's ALL speculation, I suspect her teams would not have fared any better if she were still here and Holly was still the Assoc HC. I'm sure they would be somewhat better, and of course Pat being the legend she is, by sheer force of will would generally get more out of her teams than Holly has gotten. And given that Pat knew she was not great at teaching offense, would have reached out and done way more than Holly has done to fix that (IMHO).
Bottom line is that we have no idea. I'm sure Tenn fans feel that if Pat had not gotten ill, and was still coaching, she would have earned a few NC's in the past 6 years, or at least made final 4's and NC games. I don't think she would have fared much better than Holly has, but the truth probably lies somewhere in between. RIP Pat Summit - she certainly had her flaws, but no one can deny she is a legend and one of the greatest to ever coach the game...