I find that the Steelblood archetype is good for certain builds but not others. A Steelblood Primalist Destined Bloodrager picking up the beast totem line is very tanky, and benefits more from the extra AC (can get up to lvl+25 or so AC while raging and pouncing eventually). Pounce also makes up for the speed difference, 50ft of movement is typically plenty.
Armor Training is a nice buff over the armored hulk barbarian archetype, as masterwork comfort plate is +9 AC +5 Max Dex(perfect for a starting 14 dex which is about all a bloodrager will ever have) and 0 ACP. And since you no longer need mithral, you can get back half your DR/- by having adamantite armor.
Steelblood does suffer from drawbacks, blood deflection and indomitable stance are pretty meh abilities especially blood deflection. By level 7, you probably have a +1 deflection ring rather than giving up very limited spell slots.
For an abyssal bloodrager, which has 8 less AC than a destined already, its not as an attractive option, and uncanny dodge/speed/damage reduction is probably better.
In short, is Steelblood a good archetype, I think yes, but it isn't one size fits all and an absolutely must take.
