very nice

Yea, I usually coordinate Aegis with my supporters / junglers.
It's not an item I go for in every single match - but when I see myself surviving for ages in teamfights (and if I'm able to kinda rush it), I often rush this one.
Going to add this to the situational section though ;)

Sorry for the double, I commented before I +1'd. XD

Great build. I agree with every core item, and while maybe I'd get Randuin's Omen instead of a second RoA, otherwise this is exactly how I Singe. :3

What really sold me on this build is Frozen Heart. I actually find it slightly disappointing that some people forsake FH for more AP or something else - it was made for Singed, if you ask me. The fact that you recognize how lovely this item is on him nets you brownie points. :D

One question: have you considered Aegis of the Legion for Singed? It isn't quite as tankrific as some of the items you have posted, but I think he's a viable candidate to carry the shiny shield. Since this is a tank build, I feel like you should at least mention it, but that might just be me.

You earned your +1, mate. :)

You clearly put some effort into this guide. Good work. The only place where I disagree is about the Rylai's.

As you point out later in your guide at higher elos they catch on sooner to the fact they shouldn't be chasing you so they won't be in the poison too long anyway. The slow allows you to turn and get them a little better and mostly I get it so that I can run behind an ally so the opponent can't catch them.
So as the tank I find it a very nice added cc for your team because in a teamfight your poison should be all over the field. A slowed opponent has difficulty fleeing from or chasing your teammates. If you put saving lives over killing the idiots that chase (and frankly, if they are willing to do that you shouldn't have a hard game) I think Rylai's can be a great item.

Edit: Also you can always run slower by stopping to taunt :D

Congratz on a good Singed guide. :D