Not even remotely close to worth it. Before even considering the raw HP loss, you're losing way too much Parry for how little you gain in block strength. Assuming a block rate of 28% with Allagan/Zenith, the increase in block strength from 28% to 30% is 0.5% mitigation. The 100 Parry is worth ~7.6% parrying rate, which is a loss of 1.8% mitigation (slightly less because your parry strength will rise because of the extra STR but still not enough to come close to outweighing the parrying rate lost).
Fun for a little extra DPS in dungeons where you're not pulling tons of stuff at once, but otherwise it's hugely detrimental to your survivability.