There are two different things involved here.
1) Orthodox Christianity’s position on heterodox sacraments, “baptism” in particular.
2) The proper form of Baptism.
The first is a discussion in and of itself. The second which seems to be what is discussed here, is a little more straight forward.
The normative manner of Baptism, as established by Christ and practiced by the Apostles, is via threefold immersion. Anything less than this, can only be rightly justified by necessity (ex. lack of water, someone was very frail, etc.)
The Latin Church, even after it’s estrangement from the rest of Christendom, continued to baptize via threefold immersion for a centuries before “baptism by pouring” became common. In the Latin Church, “baptism by immersion” continued up until the sixteenth century in some places.
Baptism by pouring is an allowance, within the Church, in cases of emergency. While many speak of it becoming normative here and there, and try to provide evidences for this (yet I’ve yet to see specific examples of this; I’m not saying these people are lying, but I’d like to see the examples), what they fail to keep in mind is that this still doesn’t make this a legitimate practice. You will find evidence of uncanonical and anti-traditional things becoming “semi normal” here and there within the various Orthodox Churches – that is not an argument for anything, save that they are atypical. It doesn’t make them “right” or “correct”. They’re abbherations, and are not to be looked to as role models.
There is no good argument for the practice of “baptism by pouring” – and even though it’s not the strongest endorsement that is deserved, even the “New Catechism” of the RCC is pretty clear, that only “Baptism by Immersion” gives the “full” symbolism of the sacrament. On that basis alone, I fail to see why the practice of pouring is being employed. How hard is it to do it the right way? To my mind, this represents precisely the bad sort of hyper-minimalism that helped alienate Latin Christianity from Orthodoxy to begin with. It’s the same kind of minimalist hair-splitting over Holy Communion which resulted in the dreadful practice of “communion under one kind” (which fortunately has been [i:31kogkjq]somewhat[/i:31kogkjq] corrected now.)