Races: Dwarf/duergar sould be decent because of certain gear availible. Giant might work too because of the ability to wear heavy armors (Who usually has good -AC bonuses)
AC numbers: No idea...
Damage reduction: It works as a damager reduction against every type of damage.
Good choice: Yes, we've seen some very successful characters using gates. We've also seen some complete failures and people who has been VERY disapointed with it.Might be that you're quite gear dependant.
Dex: I believe it has been said that it doesn't make use of dex bonus.
As I stated, all of this might be missinfo. But these are the things I've read/heard over the years.