There is a maximum effectiveness each side provides (15%), but I don't think it stacks well with much of anything. You're better off choosing a Spec Mastery that increases your stats/offense/defense further if you chose specs that feed off of it.
I know from testing that in a hybrid melee/ranged character with STR PSS and Enrage, the DPS parses slightly higher with STR mastery than Vindicator. The damage boosts provided from Vindicator are additive and can become greatly diminished by the Cryptic math that determines final damage, whereas STR mastery provides both additive (Enraged and melee) and multiplicative (offense) bonuses.
As CB stated, I believe most other applicable masteries are likely to be superior to Vindicator.
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As CB stated, I believe most other applicable masteries are likely to be superior to Vindicator.