I noticed that math font scales properly even when saved in a different resolution. So a temporary hack (until ParaView gets a fix) would be to edit axes and color legend font formatting to something like $%.0f$. This setting is available only in the advanced options (made visible by clicking the gear icon).
Actually, the edge lines and contour lines also do not scale properly. A fix for this to render them as 3d tubes is suggested here: Axes label do not scaling righ when save the screenshot at higher resolution. - #2 by liangwang0734.