Tier 3 dots is actually garbage

[Karl]

So I like the design, but somehow it covers less space and less consistently than the tier 2. Dots is already one of the less consistent forms of evidence and now it works even worse, just use the tier 2

[Maya-Neko]

consistency of DOTS mostly comes down to player positioning, as you can guide the ghost to it when standing within the ghost room. I've yet not seen that much difference between T2 and T3 with the only exception of T3 being more effective in large rooms due to being able to cover like twice as much area than the T2.

As for the tiers, that's pretty much what it is all about. Just take the one that suits your playstyle most. The T3 will get a buff eventually though, where it will be possible to stop it from moving, making it more usefull in narrow, but long rooms.