OP, a very easy way to test this for yourself is to fester when it appears as though you have less than your full dots up (even though you know you cast all three). If your fester damage is consistent with your usual fester (with three dots), then you know that your dots are on the boss... just 'invisible' due to the 60 debuff limit that others have spoken about. Anyway, I can confirm that this change was done in an update months ago because people were complaining about not getting credit on FATE mobs, and also because people were worried about CT having issues with debuff limits due to the reason you mentioned. But, this is fixed. You just can't see it. It does get a little frustrating if you don't know the timing left on your other dots, but if at least one dot is up you can get a nice ballpark idea of when you need to recast. When Bio 2 reaches about 18~ seconds left, you can recast your dots for full uptime.