For the sake of compactness I'm going to use normal+ to abbreviate normal, aggressive, very aggressive, and berserk, and defensive- to abbreviate defensive, very defensive, and coward.

Currently tactics gives the following bonuses when leveled up: +1 to hit in normal+ at levels 2, 4, 6, 8, ..., +1 to damage in normal+ at levels 4, 8, 12, 16, ..., +1 to DV in aggressive+ at levels 10, 20, 30, ..., +1 to hit in defensive- at levels 5, 10, 15, 20, ..., and +1 to damage in defensive- at levels 10, 20, 30, ... .

The problem I see with the scheme is that defensive tactical stances become completely obsolete at high levels of tactics. At level 10 there is no longer any point to fighting in the normal stance because aggressive has no DV penalty, at level 20 there is no longer any point to fighting in the defensive stance because aggressive also gives +1 DV, very defensive becomes obsolete at level 30, and coward becomes obsolete at level 50. Essentially, the more you invest in the tactics skill the fewer options you have - plus it makes no sense that fighting in an aggressive stance can eventually (by level 30) be safer than fighting in a defensive stance.

I think a simple fix would be to instead give +1 DV to all tactical settings every 10 levels - I don't think this would make defensive stances too strong, since they already gain bonuses to hit and to damage at less than half the rate of aggressive stances.