The respective advantages of these DoTs (compared to sticky single target /other AoE dots) are:
1) they can be preloaded from a safe position without being in line of sight of the target
2) they can not be cleansed
3) they are mobile
4) AoE
5) Blade cloak is the only non-static weapon ability that procs glyphs from the backbar.
Considering these benefits it is reasonable that they do not get the same tick rate as static AoEs.