You must be an incredibly lucky roller. Whenever i've gone out trying to keep the XI streak I've spent most of the time rolling. Plus with parties that tend to move around alot from one NM to the next, there's lots of times for the chain to break and you need to roll up and XI. Plus since I am invited to buff (I only play COR in non-Abyssea events largely since I don't have WF yet), I feel obligated to keep a miimum 3 roll rotation up and usually 4 or 5 rolls. And since players frequently move, asking them to stand still while you bust through 5 attempts at hitting XI is comical.
If you are WF/QD COR in aby just using Wizards and Tacticians roll, then I can see it being not so hard to do the XI chain. I think that is a specialized situation.