You literally have to go Catalyst at the start if you don't wanna be OOM every 10 seconds. I tried this build today and I was so much weaker than a normal RoA->Boots of swiftness->force of nature-> items as needed

This is a great guide, but i have only one possible change to it. Switch the giant's belt at start for a catalyst. You still get 1163 hp, which is only about 40 under your initial build, yet you also get the 700 mana that it helps provide. Your staying power at top is increased, due to mana, and your hp is only slightly decreased. If you also factor in the healing that is done whenever you level up, this is a VERY good start for singed.

In short, great guide, but switch the giant's belt for a Catalyst. It also helps you build into a ROA faster (which solves ALL of your mana problems)

Not a fan of rushing Rylais because you will not be able to sustain Poison Trail. You have to build that mana pool up, especially in the early game. Maybe go Catalyst into Rylais if you really don't want ROA, although your Singed will not be as great without ROA frankly speaking.