Rune shards give a disproportionate advantage toward offense over defense
9 AP: 217.5g
5.4 AD: 210g
10% AS: 250g
average 5% CDR : 133.3g
6 AR : 120g
8 MR: 108g
average 50.3 Health: 145.9g
Add on top of that the fact that early damage means a much stronger last hit potential, and that point-for-point damage outscales defenses heavily -- 200 AD and 80 AR vs 80 AD and 200 AR guess who wins that tit for tat. Going further is the fact that defenses are worthless against the opposing damage type but more damage is always better.
Final point, the gold value of defeneses is lower than the value for health until champions have 1500 or more health to begin with, which doesn't happen naturally until around level 12 and the 60 or so health from the health rune won't speed that up to any meaningful degree.
And that's all without going into the abysmal named runes in resolve compared to the offensive trees or the tank itemization that has been shit since season 7.
or mage
the intended tank runes are fucking useless