CA Indian Casinos
I live within a 2 hour drive of 8 Indian casinos in CA, and I frequent a casino once every two weeks. Based on this, I can provide my insights to your questions:
"blackjack at Nevada casinos is better than in casinos on Indian reservations?"
IMO, the Nevada casinos are better bankrolled and experienced against a host of BJ conditions. Most of the equity in an Indian casino is still small when compared to the established Nevada concerns, some of which are publicly traded.
"I have wondered if there are any legitimate suspicions of unfair blackjack games on reservations"
I don't know all the details, but I've heard the programmer behind Wong's update BJ software is involved in such a case. With regards to my personal observations, most bj games have limits of $5 to $100 or $10 to $200 which limits a spread to 1 to 20 when playing one hand, which is not a big spread to overcome 6D H17 games with poor penetration. I highly doubt the casinos I've frequent would engage in questionable behavior since the rules are so bad, house edge is at least 0.60% off the top for a BS player, and the average player doesn't know the correct BS plays.
On a separate note, since the Indian casinos want steady revenues and associated income, I believe they offer a disportionate amount of slot machines and a token offering of BJ tables. Another reason for poor BJ conditions in Indian casinos is the day trip mentality, which favors slots.