The idea behind this build is to basically find the middle ground between auto attacking enemies to spam abilities and using said abilities to buff your teammates. Tyreal has VERY good auto attack speed for a warrior and its a big part of making him function well in fights.

Level by Level:

1) Increases your regen out of combat.
4) Buffs your regen abilities (all of them) as well as healing received.
7) Reduces the cooldowns of all basic abilities
10) The equivalent of an Uther D Shield but in one spot and can affect multiple allies.
13) Turns lost shielding into gained health
16) Buffs the shield by a percentage. The more allies you shield, the stronger it gets.
20) Adds one second and damage to your allies in the sanc area.