Despite their shields working efficiently - the dominion weapons were't slipping around the shields by technobabble, but punching right through them.
Isn't this more like the definition of the shields not
You see, shields were established to have an upper limit to what they can withstand - even if they're efficient at stopping/deflecting what is used against them.
In "Call to Arms", it's UNAMBIGUOUSLY established that starfleet shields can stop dominion weaponry efficiently.
As I said, beyond that point, the dominion weapons weren't slipping around the shields by technobabble, but punching right through them.