I have little Dr. Who knowledge, but I suspect that the intelligence factor is going to be the decider here.
Simply put, the intellect of the Borg is described by two maxims:
1. Nobody is as smart as all of us.
2. Nobody is as stupid as all of us.
The groupthink would be their undoing, as being attacked by too many geniuses at once might well end up breaking them (or at least stalemating them), particularly since it's entirely possible that as the Borg adapt to new things they may be rendering themselves highly vulnerable to already-adapted attacks. I could see the Daleks leading the Borg around on a merry goose chase along these lines.
Plus frankly the Borg are far too single-minded. Their strategy for invading Earth:
Collective: We want to assimilate humanity. Let us assimilate one of their greatest to facilitate that and learn of humanity.
Picard: Humanity will resist assimilation to the last man or die trying.
Collective: Obviously despite current evidence strongly to the contrary the correct approach is to show humanity a forcibly assimilated member of their species preaching about their powerlessness to avoid this fate. Surely this cannot possibly backfire, reinforcing humanity's revulsion at assimilation, encouraging them to create powerful technologies to destroy us, and turn our forced informant into our worst nightmare. Right?
The ones in parting of ways clearly diod yet they still get blown up. Dalek sheilds are like any sheild, hit them hard enough and they go down. Why do you think the entire power supply of Jack's gun, (which by the name is probably a really heavy duty personal side arm for use agains't the general species of the galaxy), the Daleks just take that much raw punch to reduce for scrap, indeed it survived the beam for a few fractions of a second.