I bought one of these last night and could've sworn that I was moving at half the normal speed in towns. Not sure if that is just a perception (since the rift warden is so much taller than normal characters), or it the tonic somehow slows you down.
I didn't think that the beetle tonic slowed you down...
Does the phantasmal tonic make you move slower?
Jetdoc
jonnieboi05
no, it doesn't slow you down. i've got an everlasting so i use it a whole lot-- no noticable difference.
~LeNa~
Covah
You are bigger, so everything looks smaller and makes it look like you are going slower I guess 
Shadowmere
it was probably just a trick of your eyes, you're moving the same speed as a normal player but with a much larger model, makes it feel like you're slower than you are. if you still want to go faster, pop some sweets and have at it!
I Can Cure Cancer
Lol it's just your perception.
Shai Lee
It must be your eyes because I saw a Rift Warden chasing a Beetle around Kamadan just fine earlier. :P