To me, 'over-scouting' only applies if I'm not actually capable of clearing out the newly scouted provinces == especially if hitting ring 11 or so when orc heads are necessary but one can't yet make them with armories or other means yet. The advantages of the expansion plots for my city far outweigh the added negotiation costs for those additional provinces, since it is a rare hard / very hard fight I can win yet -- my combat skills aren't quite up to snuff.
Extra bonus ... more provinces scouted / cleared = more potential tourney provinces available each week.
I started to skip optional squad size tech when I learned that it had a negative impact to my tourney potential.
Being mainly a producer and not a fighter until mid Fairy chapter, this approach worked well for me = in addition to taking advantage of a couple 100% diamond promos for builder / magic academy and then diamond expansion plots.
Getting boosted good production bonus to max levels as soon as possible helped me more than any other single thing within the game -- the excellent advice, tips, tactics and thought provoking strategy approaches from the forum community is a class all its own.