Queensguard can be tricky to deal with, that's true.
There is multiple counter to that game plan though, one of them being, if you manage to take the first round try to force your opponent's priestesses/Sigdrifa out of their hand, even reducing their options to Sig is a good thing because it would mean that they can't buff their QG another time by resurecting Draig Bon-Dhu or playing Holger BH if that's their plan.
Another thing to know is that, the QG represents the most part of your opponent's power, if you're ahead on points after they're all out you shouldn't release the pressure, it's unlikely that your opponent can race you from that point (be careful though, unlikely doesn't mean impossible, they might still have quiet some tricks up their sleaves, but the QG is their win con by nature, it's not good for them if you can beat them on board).
Besides that taking down one QG out of the 3/4 is also a good plan, it rarely worth wasting a priestess to bring a single one back, it's such a slow tempo play.
AoE also helps (Lacerate, Arachas venom...), you might considere finding a spot for those spells in your deck, especially considering that they would help you a lot against Monster Swarm as well. And yes, your opponent could run some Armorsmith or D-Bomb but it's not very commun anymore (I do play with one D-bomb myself but it doesn't seem to be true for most QG players nowdays). Furthermore, if you force a D-bomb on your opponent's QGs at least it won't end up on your Spotters, which can't be a bad thing for you.
Strangely enough Mardroeme isn't a good card against QG, weakening one of them doesn't achieve all that much, especially since it implies you to not add any strengh on board when you use it.
About the mulligan, I found Aukes quiet poor in this match up (except if you're facing an hybrid discard/QG deck), I usually don't want him in my hand. Peter is slightly better, not ideal but he can help.
On the other hand Vanhemar (if you play him in your deck) is a premium card against QG. Not only this deck usually don't like weather (unless you're facing some very specific situations, always put frost on the front row, this is where all you're opponent's power will be) but Stammelford's tremors is really potent as well, killing the Priestesses in one shot and damaging the rest.
About the medic, playing 3 is obviously too much but maybe one could fit in your deck (I don't now your list so you're the only one who can know for sure), also see if Assire can help you with your strategy (she's good with Roach for example).
And to answer your question, no, locking the QG doesn't help at all, the QG card reads "Deploy : Resurect all QG" meaning that, even if a QG is locked in your opponent GY she will still come back when your opponent play one from their hand (she is the one who bring her friends back from the dead, not the other way around).