Zebo's been at fullback and has been making some fantastic covering tackles, Earls has had Taute and been playing at a much lower level than international, Ringrose in his first real start in a tier 1 international is a different prospect. There's plenty of reason to worry considering last time out every in road was made by Aus down Zebo's channel and one of the few times Earls has had to defend an actual overlap this season he got himself sent off and lost out on beating NZ... The reason Munster are so good defensively is not because of their wings, Zebo's covering is part of it but not something you get to do as much at wing. Add to this that v Canada Schmidt had it set up that Earls would defend set pieces inside Ireland's 22 from fullback, which he did badly/didn't bother doing for Canada's 3rd try, and there's plenty of reason to be apprehensive of three guys who haven't proven their defence at international level. The fact one is replacing Trimble adds to this completely.
Muff - On Ringrose, no its not an issue, BOD got rinsed a few times early in his career, its to be expected and is why I want strong defenders outside him.
On Munster I've watched plenty, they're doing fantastically well against what has been put in front of them and that's why all the borderline calls are going there way, except maybe Scannell v Tracy which should go their way. When you consider that the best team they have beaten this year is Glasgow (x3, 4th in the pro 12, they beat Leinster and O's reserves) we should get on fine this weekend but if that was the team to be played against England or France who can really attack the wide channels and have a much better chance than Scotland do of matching us up front I wouldn't be comfortable.
On stats - I don't think that says a lot, Munster's defence has been the best of the provinces this season so that'll happen, its easy for a wing to defend when the defence is set wider than the attack and dominate contact while doing so. Its also based on what? Tackle % and points scored against them? Positioning, decision making and exit play won't come into them which are equally important.
On Ryan - he's a good player but we have three THPs at his level and I think he loses out to the other two marginally.
FWIW, I think they're the two guys to start this game, what worries me is that I don't think a slam is achievable umless Trimble comes back, Bowe finds form of old to displace Earls or Ringrose becomes a defensive God under Schmidt.