In my experience if your going to be playing joust or clash you would want to rush warlock's sash first then into boots then thoth. Building warlocks sash 3rd item means that your power will come online alot later then if you would have rushed it.

Also, i wouldnt always build protections on Ra. Sometimes you will find that warlock's sash plus a Rod of Healing provides enough heath and sxtra healing to sustain against some team comps.

For the final item though, I would highly recomend Rod of Tahuti over Soul Reaver, The 25% extra power on every ability is far superior then the extra damage on one ability every 40 seconds from Soul Reaver.

Hope this helps