The intuitive thought is that you want to be calling with your lower pocket pairs, since you want to see flops as cheaply as possible. But if you are always calling, and never 3-betting this would tell someone a lot about your 3betting range.
Is it correct to assume that always calling in Position with lower pocket pairs, and then defending with a mix of calls and 3bets in the blinds is a better tactic than always calling / folding?
In a word, yes. Calling in position is always better, if you think you will not get 3-bet, or especially if you are last to play.
Mixing it up as you described above is, IMHO, the best way to play these. Combine this with adjusting to the dynamics of the table and smaller PP's become a bit easier to play.
I will sometimes raise 22 UTG, and 3 bet or call a 3 bet with it. But, say, a raise UTG, a 3bet from anywhere and I am still to play, my 22 are gone.
Since I never open limp unless I plan on getting raised (I know, never say never, but still...) any PP will be an automatic raise if I am first in (or any hand I am gonna get involved with), and my calls and/or 3-bets will be mixed up depending.