I agree that the base complexity given (weakest of NPC/PC's lore/disc/conv + any enhancement bonuses) is weak tea... most of the time, a dedicated caster's gonna end up with Wards:4, and while that's technically on par with battlefield weaponry, it's at the low end of the scale (barrett .50 cal), and I typically think of Dresden's wards being more on par with a main battle tank.
Reflective Wards ought to be tough enough to be able to bounce any spell the caster would consider threatening- and maybe a skosh more... which most likely means he'd make it strong enough to bounce anything he could throw at it. (Not many people who don't own guns bother going in for kevlar.)
Land-mine wards are pretty straightforward (deal weapon damage, no real accuracy bonus that I can imagine)... and just raw Weapon:4 w/ no accuracy bonus seems low to me for the descriptions we've seen of such wards (typically designed to be able to seriously harm to some pretty big, bad things)... but the base complexity is a decent starting point.
What I'd do:
For the barrier/border/reflective wards, set it up at a total strength roughly equivalent to his most-used rote +2 (so that it'd bounce what he has to offer even on a good attack roll).
For the land-mines, use the base complexity, and then for every +2 to the strength, give the players an FP in a group pool.
Anything else you apply in the way of features (in the theme of land-mines: spells set up to go off when the ward is attacked or breached, but not direct damage... like for example, a ward that veils everything inside when breached), use the same total strength as the land-mines or the reflective wards (pick one)... and give the player pool another FP per such feature.
This way- the wards are a bit more appropriate to the wizard's power level, but the players get some FPs to help pay for the extra complication/threat (complication due to extra features, threat due to deadlier land-mines).
They'll probably need them.