The Tree Herder I ordered came with a 75mm base … but according to the book and photos on different websizes I would have assumed it has a 50mm base, is that correct?
(Or could the included 75mm base size be a “hint” for a future rule change or has the bere some rule change since 3.0 release that I missed?)
Any input appreciated 
more likely it’s just a mispack, you should pm Mantic’s customer service for another. It’s supposed to have a 50mm and that’s not going to change for at least an edition
It’s a monster, so 50x50. Only titans and Hero (titans) use 75x75.
Thanks @Vince and @Gerrcinn. I got several 50mm bases laying around so it s no problem. Just wondered as I saw the 75mm in the box 
It’s a bit of squeeze fitting it onto the 50mm base, so 75mm seems right for the model, but it’s 50mm in game, so I would use that. You can put it on a bigger base if you want to (Exceptional Base Sizes in the rules), but it’s almost always a disadvantage in gaming terms.
Mhhh good point @Edzig, but now I’m wondering, … would base size affect aura size/range as well then?
Good question. Yes, I believe it does, so there is some advantage to be gained from a bigger base size. On balance, I think you lose more by having your herder easier to flank and multi-charge than you gain by having a bigger bubble.