You make some good points, but I can't agree with most of what you say here. Granted, you probably have more experience with Morde than I do, but in my personal experience, I can't agree with rushing FoN, or Warmog's. You're saying don't rush Tank items, but that's exactly what those are... full-fledged tank items.
All of your build relies entirely on base damage and hopes the other team doesn't build any MR at all. I never suggested rushing tank items, I suggested focusing on items that add Armor, MR, CDR, and Magic Penetration. Randuin's Omen's side effects are much needed CC, allows you to AoE slow the team, and CC's anyone who auto-attacks you. The CDR and Magic Penetration ensure that you're doing **** near True Damage to anyone without any magic resistance, and thus boosting your shield regeneration.
You only get just under 10 Magic penetration from runes... this is NOT enough. Most Champions have around 30-45 MR without items.... IF you buy Abyssal Scepter (which is not a core item... nothing on my list is), plus Sorc Boots, you've taken out 40 MR right there.
As for Frozen Mallet/Rylais... I stand by my point that it's preference. Everything you've mentioned is absolutely true. Frozen Mallet however requires you get within Melee Range (or pray you can grab a ranged pet)... and when someone is running away from you, you have no chance of catching them. Unless you build Boots of Swiftness and have FoN... well then yea, I suppose that's a different way to look at it. The Sorc Boots just add too much to your overall damage output (and consequently, your shield regeneration) to pass up in many games.
I'm not denying that your build doesn't work, in fact I know it does. I just know that when I'm facing Morde's with your build... I tell my team to ignore them, kill the team, and then turn around and beat him down - or just watch him run away from the 5v1... 4v2 if he's lucky. Without CDR or Magic Penetration (in addition to runes), Morde's damage is laughable to anything but a squishy who builds no survivability.
As for Q, well, I have been trying to get it earlier, and in some situations it has been beneficial to obtain it sooner. Once again, that goes with the theme of the guide to remain flexible. Regardless, the earliest I'll grab it is at level 4. It will stay at 1 point until everything else is maxed out.
Oh, and I have Guardian Angel as something to avoid, not something to consider
EDIT: If you do love that much HP, do me a favor, just for one game. Go and try a full HeatnServe build for a game:
- Doran's Shield
- Aegis or Spirit Visage
- Sorc Boots
- Frozen Mallet
The first time I did that build, I had my best game ever at the time. Then I started looking in to why, and how to further maximize it. Through research and experimenting, it came down to the heavy focus on Armor and MR, the CC from FM, and the heavy AoE damage. This build works in most games... but obviously not every game, because there is no core build for Mordekaiser. Regardless, it gives far more effective HP than a Warmog's build.