No !
Thats pretty low defense for an eth armour. Mercs have decent strength so you do not need to use a low strength armour. Look for armours up to Lacquered Plate (strength req 166). You should not consider using such expensive runes without at least 800 defense. It's ideal to get superior eth armour too.
Look for unsocketed eth armours, and use either the cube recipe (which is very cheap) but gives you random number of sockets (getting 3 or 4 is what you want) or Larzuk to guarantee 4 sockets.
I have an eth superior Kraken defense 848 I have not used for stone because I think the defense is not high enough.