Connecting the DoTs: A Summoner Guide

[KaedrianLiang]

my dots are falling off quite often on raid bosses in 24 player content. Is this an issue only for me or the gamed design?

[Havenchild]

my dots are falling off quite often on raid bosses in 24 player content. Is this an issue only for me or the gamed design?

Both?
So basically there is a limit to how many DoTs you can have on a mob and a limit to how much you can actually see.

The actual DoT limit is 60, while the visible limit of debuffs is 30.

So if you can't actually see your debuffs, it may be you let it fall off passed 0 seconds and when you reused it, it may still be landing or it may not depending on how many DoTs are currently active. So after your initial DoTs, if you want to still keep them visible, you have to make sure to refresh the timers before they hit 0.
Or you can change the option under Character Configuration to only show when your DoTs are active but this disables all buffs/debuffs you do not inflict including buffs like reflect damage that bosses use.

Other than that, DoTs don't just fall off.