Well, everyone's entitled to their own opinion.
a tank for example when it lists all +Def enchants when that is not always the way to go
in this case, you would get some low score for +def enchant, because even some defense enchant is better than no enchant. However you get higher enchant scores for some more useful enchants, like +6 stats, or 150hp, etc etc, depending on a slot.
Enchants and gemming is totally dependent on what stats you are currently lacking in, for example once you are uncrittable then you should obviously start stacking avoidance and this site doesn't recognize that
Avoidance is useful up to some point. If you have very high avoidance but low hp, you're dead, also if you're a warr for example you won't get enough rage to maintain required threat. But who can decide how much should you boost avoidance and how much other stats? It's individual, it represents your play style. It also depends on a boss, on some you need high avoidance, on some you need hp.
If you want me to take a closer look about those "bad things", link your zone, realm and character name and I'll be more than happy to help you and "fix" the problems