Jeremy,
The Hebrews text (10:30) does indeed quote the LXX of Deuteronomy 32:36, which translates the Hebrew din as krino, which means "judge." There are two points you need to consider, however:
1. The primary meaning of din is "judge" so the NIV is perfectly legitimate. In fact, according to BDB "vindicate" is a third-level possibility for translating din. It is a possibility (I do not deny that), but not a primary one.
2. The author of the letter to the Hebrews saw fit to use the word krino here, not dikaioo (to make/declare righteous, or vindicate), which would be closer to what you presume the verse means. You must deal with the Hebrews text as is, which the language used there. Even if your exegesis of Deuteronomy 32:36 is granted (which is a sizable "if" - yes, God is speaking of His enemies here, but note the use of the pronoun "you" in v. 38 - He is including His people in the judgment), you must still deal with the fact that Hebrews 10:30 says, very plainly, "The Lord will judge [not vindicate] His people." "Vindicate" there would make little sense, in light of the fact that the context is threatening judgment (not comforting the regenerates there, as you said).
The Hebrews text (10:30) does indeed quote the LXX of Deuteronomy 32:36, which translates the Hebrew din as krino, which means "judge." There are two points you need to consider, however:
1. The primary meaning of din is "judge" so the NIV is perfectly legitimate. In fact, according to BDB "vindicate" is a third-level possibility for translating din. It is a possibility (I do not deny that), but not a primary one.
2. The author of the letter to the Hebrews saw fit to use the word krino here, not dikaioo (to make/declare righteous, or vindicate), which would be closer to what you presume the verse means. You must deal with the Hebrews text as is, which the language used there. Even if your exegesis of Deuteronomy 32:36 is granted (which is a sizable "if" - yes, God is speaking of His enemies here, but note the use of the pronoun "you" in v. 38 - He is including His people in the judgment), you must still deal with the fact that Hebrews 10:30 says, very plainly, "The Lord will judge [not vindicate] His people." "Vindicate" there would make little sense, in light of the fact that the context is threatening judgment (not comforting the regenerates there, as you said).