What are your thoughts on the Archie Moore/ Joe Fraizer type cross armed block?

Well since they brought this tactic to the game, they were probably best at it.. I think it is obsolete today but still seen from time to time. I also think that it limits your options to counter-punch since it is truly a defensive measure.. I have used it successfully a few times but only as a last result when I faced a heavy-hitter. The "up-jab" wasn't popular back then while the Cross-armed block is becoming obsolete today. Techniques change with times and styles. Hope this broadens your opinion about such a tactic.