OK, I'm going to go through these one at a time, so it will be a long post.
First, Zenirix shouldn't have three heads, it isn't made to look fierce, it's made to look like a loyal companion dog.
Official Zenirix deion: The Zenirix is a loyal Creatu by its very nature. One which is raised from the egg will stay with you to the very end, becoming devoted a companion through thick and thin. When left in the wild, they will find others of their kind and form troupes for safety and fellowship- for without socialization, it is rumored that these pleasant and cheery creatu will perish. They love attention and will give you nothing but respect if you treat them right, so it is no wonder ranchers and merchants have been befriending them for ages.
All of it is important but the part I bolded is especially important for this argument. They are pleasant and cheery, three headed cerberus-like dogs don't give off that impression.
Official Tesuri deion (part of it): ..feathery wings and soft blue fur...The Tesuri's amazing learning ability and unique beauty made it a very valued pet by the Scrians, but because it had so many predators, it was rare to ever see one...These talented and loving Creatu...
It has feathery wings and soft blue fur, it says that right in the deion, I don't know how you would make something that is supposed to look so gentle a demented creature. The second bolded section tells us that it is not a predatory creature, so why would it look like a demented dog? That would make it seem, once again, more violent than it is. Also, it is a loving creatu.
I don't know what to say about the Roditore, you're suggesting not changing it at all? I don't get that one, you're saying it should look "like a meerkat or this rodent-ish type thing like it kinda already is," that's saying it just needs an art update? I'm not gonna touch that one. I agree the Roditore needs an update, but I'm not going to figure out what you're asking for beyond that.
As Yaizhbeen already pointed out, the Uilus fits the Griffin deion quite nicely. It isn't exactly what you suggested, but it's already a griffin.
With the Goiba you seem to have deviated from your demented-looking preferences and have gone with the cute one. The Goiba is a powerful, ancient creatu related to the Murren, it doesn't have to be really cute. Actually, for the most part, adult creatu aren't all that cute, with some obvious exceptions. The Goiba is one of those that isn't. The baby form is quite cute, and as long as that meets the cute criteria, I don't see why the rest of the stages have to be cute. Have you ever seen a cute oyster/turtle-looking thing?
The Otachie was just revamped, so it's a little early to be asking to revamp it. It is a silent glider, according to the deion, so fuzzy wings not only would be detrimental to flying, but also to the silence. Overly feathery wings might make it louder, not good for a predator. Besides, the wings are already quite feathery, any more and it would make it hard for any animal to fly. We've already had a few "make the otachie look like a lion/tiger/other big cat" threads and none of them have really done well with the staff, so I don't think that's happening.
The Mirabilis, as Yaizhbeen also pointed out, is already a majestic bird. A little in need of a revamp, yes, but again, as Yaizhbeen said, probably on the artist to-do list after the new creatu come out.