Rationale: to dispell my 10 "death wards" the caster dispelling would then need to roll 10 times.
That is true, but it comes with two problems:
You have used 10 spell slots of level 4 or higher to prevent one 3rd level spell from working. Spell that may not even happen. Probably there was a ton of other things to do with these slots.
You need a whole minute to prepare, and then have relatively short time it works ("Duration: 1 min./level"). So you need to be certain fight will start in the rather narrow time window, or you don't finish your preparations, or it is too late and instances of your Death Ward starts to time out and go to waste.
Spells with longer duration would work better in that regard, of course, but that limits valid choices for your strategy pretty severely.
Thus, while there are no artificial limits to how many times you can cast Death Ward on yourself, casting it many times quickly becomes too expensive to be viable. In a niche situation when you know that Big Boss loves to dispel and cast death spells, this may be viable strategy, but most of the time, it is not.