I don't know Vanderklok and it's always impossible for us to really have any insight on what the assistant coaches are doing or how they relate to the players. But some things I would comment in his defense:
Our goaltending results have generally been very good overall during his 5 or 6 years, culminating in a Vezina trophy win by Pekka. Mitch Korn was one of the pioneers in goaltender-focused coaching in the modern era, and certainly none can deny his track record and legacy. Part of what he helped to accomplish was a blossoming of goaltending knowledge and progressive instruction all through North American hockey, at all levels. There are now A LOT of very knowledgeable and capable goaltending instructors out there. But I would suspect that in the course of 15 years of observing Korn at work, Poile was able to gain at least some understanding of how to evaluate the capabilities and requirements of that job description. Taking on Korn's young understudy may have initially been just a natural progression, but 5 years later I would think Poile would have had ample observation of Vanderklok's methods by now to allow an effective evaluation of his performance. And he hasn't been found wanting by those who actually do observe him and work with him.
I tend to find that the most distinguishing trait of a goaltending coach is simply their ability to get along with the player. That they are on the "same wavelength" and just have a knack for communicating and understanding eachother. Like I noted above there are now quite A LOT of really good goaltending instructors out there who have studied all the available technical material and attended all the symposiums. But once you have that level of book expertise accounted for, the really important part is the personal relationship with the player. And I would further submit that Pekka Rinne has been salaried for something on the order of $50M with unheard-of-in-Nashville NMC clauses in his contracts. Pekka Rinne is a valuable organizational asset, represents a massive investment of resources, and I would submit that he would certainly have the power to request a different coach if he was not 100% satisfied with Vanderklok and if they didn't have a very strong relationship. Rinne has had good goaltending coaches in the past and is well known in his native land as well - if there was any question whatsoever of finding him a better fit as a coach, I'm sure the team would have had no trouble bringing in one of the Finnish innovators or finding some other highly-touted candidate. But they never have done so.
So where I'm going in all of this is that the people who I think have the best vantage point for evaluating Vanderklok - Korn, Poile, and Rinne - would all seem to be fully vouching for him. One year of shaky on-ice goaltending results - a year in which many other aspects of the team have also been off-kilter - doesn't seem like enough to outweigh this. From our limited vantage point as fans, maybe taking that as evidence seems circumstantial - but in reality, for the people who really matter within the team structure, highly experienced professionals in their own right - they have all the real evidence in plain sight to evaluate. To me, it would take a much larger sample size of fan-vantage evidence (i.e. on-ice results) to challenge the internal evaluations for a position like goalie coach.
Not to say it's not a worthy topic of discussion... everything should be fair game here. Definitely worth asking the question. But it's such an impenetrable part of the team operations to us, it would really take a large burden of on-ice evidence for me to really get further invested in questioning the goaltending coach. This half-season of shoddy goaltending results in the midst of overall team turmoil, with one aging and potentially physically declining goalie and one young understudy trying to overcome his deficiencies - it's not enough to make me question the judgement of Korn, Poile, and Rinne on this one. If they say Vanderklok is good for them, then I would take their word on it.
