I'll also note that since Physical and Magic armor are separate, you'll need either need to heavily invest into both of those at the expense of other stats (this is a particular challenge for FIN-weapon-users), or else neglect one of them, in which case you won't have the extra armor anyway.
Thought experiment, then. If CON is basically worthless for survivability because armor is better, then if in addition to the +7% health, CON also gave +1% Physical armor and +1% Magic armor, would it a) still suck, b) be no better or worse than STR/INT, c) be too good compared to STR/INT?