I am a bit late but I am finally getting to my Ad Mech review. So instead of a wall of text I have decided to break it up into a few different posts. Since the Forge worlds are this biggest change in the codex, each post will feature two forgeworld and I will give my thoughts on their Dogma, Warlord Trait, Stragetems and relics.
The Graia dogma allows models who die or fail moral roll a D6 and if it rolls a 6 it stays in play. It is nice but does not help much. It might help a few guys survive throughout the battle but it is not something to count on.
Warlord TraitThe warlord Trait is interesting. If a unit is engaged and within 6" of the warlord they can fire assault and rapid fire weapon at the closest model. This will be nice since most of the units are more shooty than punchy this will help them dish out some pain to those who charged them last turn. While I don't usually get my guys into combat, it might help out get out of a jam when they are assaulted. Again I don't think it is something to count on.
StratagemFor 1 command point, the Stratagem allows a unit to roll a D6 and on a 4+ it ignores psychic power that was cast. This is the only reason I see for using Graia. If you are in a psychic heavy Meta you might want to use Graia.
RelicThe relic cerebral techno-mitre grant you
The Metalica's dogma will help units move across the board while not losing effectiveness in shooting. Units with this dogma don't suffer the -1 penalty for firing assault after advancing as well as treating rapid fire weapons as assault weapons. This is handy when you are moving about trying to get objectives you can still shoot most of your weapons without penalty. While not awesome it is handy.
The warlord trait allows units within 6" of warlord to fall back and still shoot at -1 to hit. this is handy and situational like the Graia's trait. This allows you to choose who you shoot at as well as leaving your opponent's unit open to fire from other units. Again I don't like to be in hand to hand with most of the Ad Mech so I try to stay out of combat. This is nice if they charge me.
The Metalica's stratagem tries to help deal mortal wounds to your opponent's unit. For 1comand point, you can pick a unit and that unit has -1 to leadership during the moral phase. I am not sure I would ever use this. Command points are precious so I don't think I would use it to maybe do a mortal wound.
I like the relic for Metalica. The Adamantine Arm is a single attack at strength times 3 AP-3 for 3 damage. This will make most of the characters S12 for one attack. It is nice but requires you to be in combat. So over all, it is hohum.