Engel is meant to just be a walking wall so it would be worth using this on him and then having an accessory to pick up his speed a bit. Using this armor and Hermes sandals if you have the honor of having them or a tmr with agi is a good choice
Engel has decent luck, which gives him good evasion. It's possible to build him as an evade tank, in which you would use evade Mythril armor. If you don't want to or can't go that route, then this works too. If the stat is maxed, it only brings down AGI by 2.
I know across your equipment only the highest stat is taken, in this case where golden armor has negative stats, do those still come out of your total stats even if you have another piece of equipment that gives you say +3 agility?
Between both pieces you have +3 agility, or would the -3 cancel out the +3 giving you 0 agility?