Hey there,
first off, are you sure you have a pair? Males are quite distinguishible from females; males have a large cluster of spines on their tailbase.. females don't.
It took me a while for my t. orientalis to start copulating. I was constantly switching things around, trying new things, until it appeared that they liked/tolerated my conditions.. as for combatting, I have not heard of this, mine have copulated and layed eggs without an additional male to combat with.
As for yours being "proven breeders", I would be a bit skeptical of the source you acquired them from. The old "proven breeders" bit has been around for a while, and is probably one of the most common pitches to lure an unsuspecting buyer into a group of animals who are either duds, or animals they became frustrated with in lack of breeding. I have seen "proven breeder" niles, savs, whitethroats, dumerils, etc.. but where are the pics of the eggs, babies, etc...??
Just give it time, try new things if certain things aren't working for you.. Learning to fine tune your husbandry is the tough part.. I am only beginning to understand some of my animals now..
I notice something that plagues the monitor keeper population. Many people buy animals hoping to breed and make lots of $$$. When they begin to find out that it can be time consuming, frustrating, and expensive, they usually pass off, or dump off their animals on the next person... People need to have more patience when it comes to their animals... Many people are out for the $$$, and when that doesn't come through, they move on to the next "money making project"...for those people...try ball pythons.. People need to appreciate their animals more, and should realize that its about the enjoyment of keeping these fascinating animals....let's get back to the basics.....
THe last section was in no way aimed at you.. I was just expressing my feelings of many monitor keepers that I see come and go. My advice to you, sit back, relax, enjoy your animals, and they'll do what they do... take care,
bob

The Odatriad