I can't answer for views expressed on the ER forum. It is not something to which I pay that much attention and, as I said before, when I visited it recently, I was not exactly impressed with the "quality" of the comments that I read.
When someone tours as much as Dylan does, you can expect the "law of diminishing returns" to apply in terms of ticket sales. For example, I know many long-term fans who might have attended, say, all the UK shows previously but won't do so this year and haven't done so for quite a few years. In contrast, MK tours much less frequently, so these phenomena apply to a much lesser extent. It still doesn't mean that Dylan "needs" MK.
Given your comment, it is still telling that it is a Bob Dylan tour, with MK in support. Amongst the comments I've heard from Dylan fans is that the inclusion of MK on the bill has driven the ticket prices up.
Please understand that my comments were not intended as any kind of criticism of (or attack on) MK. Having probably attended more MK (and MK-related) shows than the average Dylan fan, I shall be pleased to see and hear both on the same stage. Apart from anything else, this touring arrangement will probably save me money in terms of ticket, travel and hotel costs (compared with two separate tours that is.
On the other hand and with regard to the ability or otherwise to fill large venues, then perhaps a double-header bill is not my preference. I'd rather catch Dylan in a small venue than a large barn or a hangar - but I'm not given that choice.
Incidentally, just as I know of MK fans who have never seen (and would not ordinarily see) Dylan on stage, I know of MK fans who do go to concerts on Dylan tours. The former do outnumber the latter, in my experience, but there are folk with wide-ranging musical tastes on both sides of this seeming BD/MK divide. For that, I am thankful.