The simple answer is: no you can't customize the multicols balancing algorithm in a way that it automatically generates balancing that matches your use case.
The balancing approach of multicols is based on the assumption that we are balancing text that is read column by column from left to right and that any excess space it placed in the rightmost column if balancing isn't able to find a split that keeps all columns in equal length. As your MWE requires that the first column holds 2 lines (minimum) the algorithm therefore generates 2 lines for the remaining columns too and that makes the last column empty.
In your example with just formulas (that may be read more from left to right rather than top down) this may not look so good. But for normal text (and that is what multicol is intended to managed) you formatting as 2+1+1+1 is inferior to 2+2+1+0.
But truth is that very short columns do not work well in either case with text and typically require manual interventions and decisions. At the moment multicol balances happily down to a single line, e.g., 1+1+1+1. But for many text applications it may even be better to force a (customizable) minimum of 2 or 3 lines even if that means some columns stay empty.
[Side remark: I see that the equations are numbered, but I would not be surprised if most people would read this left to right and then surprised by equation 1. followed by equation 3. have to rescan. Don't think that this is a very effective way of presentation. So maybe this format should be replaced by a more a horizontally oriented approach (via
longtable or the like).]