re: Lord Xia.
You seem to be confusing races and empires. they are quite different things. Most of the things you've pointed out are EMPIRE abilities, not race abilities. You specify "RACE" in allcaps as if you're trying to compare the racial blood abilities. Yet not only are you mixing empire and race abilities, you're also leaving out many empire abilities and judging empires based on only the (incomplete set of) things you mention.
The "Amarian" race is the primary race of the pariden empire. And on top of what you mention, they also have the ability to summon outposts anywhere for a mere 50 mana which gives them incredible landgrabbing power earlygame (which as we know, is the most critical time), the ability to cheaply buy spellbooks for their heroes (enabling your soverign to not bother taking spell disciples at creation, and thereby granting an extra 2-4 points) and the pretty decent sindarian staff, which allows very useful early melee troops who have decent dodge and damage, without any research into the military path.
That aside, i think the amarian blood ability is pretty darned good. especially when you're lucky enough to find tons of air mana. in a pariden game i played recently, i ended up with 7 air shards, and i won through having an entire army who got double turns, and heroes with triple turns thanks to ridiculously powerful haste spells. (which of course EVERYONE had thanks to yellow spellbooks)
Again with "wraith", you're thinking of the resoln empire. Again you've mentioned only a racial ability, yet compared them to other races' empire abilities. The resoln empire also has the ability to spawn tons of free units from mana shards, and a set of four fairly-good unique spells, the most notable of which is graveseal which makes wiping out dragons ridiculously easy. Their corrupt ability to convert mana nodes into death mana is pretty good too. it would be better if shadowbolt wasn't broken, but that will be fixed i'm sure.