They never wrestled each other often, but if I remember correctly, they had more matches against one another towards the end of 1998 to 1999, and they were usually a superior series of match-ups, with Taz usually winning as it was coming towards the end of his run in ECW.
for the most part, they were the top 2 stars in the company, but with the overflow of people they had wrestling for them in a 1 hour show, it made more sense to have them headline different divisions, as RVD was the longest reigning TV champ, and Tazz had several long runs as ECW champ.
They never wrestled each other too much, but they both were the SH^T back then. RVD's cool now, but sh^t, Taz was KILLING people then!
I don't know if it was necessarily that often but they did wrestle in Taz' last match there. And I do remember them being partners on a few occasions