I like Entropy, primarily on bruisers. Phage is kind of OP on all maps, so a more aggressive upgrade (rather than the more defensive Mallet) is really good on champs that scale with flat AD (again, namely bruisers). I would honestly like it on SR too, but that's probably not a good idea for balance.
Kitae's... I dunno, it's like Xypherous said in the other thread. Since bruisers generally have no more than 50% more HP than squishies, but much MUCH more resistances, magic damage % of max HP isn't a very effective pick against bruisers. I feel like an item that is ACTUALLY more effective against bruisers would be... maybe something that converts part of your damage to true damage rather than doing percent of max health damage?
If Kitae's is just supposed to be another onhit item (like wit's end, ionic spark), it should probably not 'pretend' to be an anti-bruiser item, y'know?