uther

Uther is a strong support which handles really well burst and crowd control but deals poorly with poke and poison like Lunara and Gul'dan . He has a stun with  Hammer of Justice , gives 15 armor when healing and can keep healing for a few secondes when he dies thanks to his trait  [Devotion, Eternal Vanguard]*  . He can solo support but is also good when paired with another support like Ana or Auriel .

Standard build

At lvl 1,  Wave of Light  gives you cooldown and refunds mana, plus you increase the passif duration once you have finished the quest.

At lvl 4,  Holy Fire  gives Uther a bit of damage and wave clear.  Pursuit of Justice  can be good when you need the movement speed like against Arthas for example.

At lvl 7,  Hand of Protection  is the way to go in most cases since you can save an ally from all cc for 1sec, also note that auto attacks reduce the cooldown of this ability.  Guardian of Ancient Kings  can good when you can make it proc often and easily like on Alarak 's or Stukov 's silence but this only gives armor and do not remove the cc, that's why you prefer  Hand of Protection  in most cases.

At lvl 10,  Divine Shield  is generally the best as you can save an ally or enable an ally (for example Genji 's dragonblade).

At lvl 13,  Blessed Champion  gives you extra AoE healing which is always nice since Uther does not heal well multiple target. Well Met   can also be good in some cases to reduce an enemy's damage (for example on  Holy Shock  Sonya or Illidan ).

At lvl 16,  Benediction  gives you more crowd control when combined with  Hammer of Justice  : if you use Benediction  and then   Hammer of Justice , then you can use  Hammer of Justice  immediately again. You can also combine it with your other abilities for more heal.  Tyr's Deliverance can also be good when you have a second support that has sustain healing like Auriel but it is much more situational.

At lvl 20,  Redemption  is the best since you can die during the fight, heal a lot with your trait and then revive.

Q build

This build is good with double support as you can use your Q spell to do damage rather than healing your allies thanks to  Holy Shock  at lvl 4.  Silver Touch  at lvl 1 gives you a mana reduction and more range so you can spam  Holy Light  on enemies after lvl 4.

At lvl 7, you can still take  Hand of Protection  if the second support cannot deal with crowd control. 

At lvl 10 both ultimates are fine depending on what you want/need to do. If you have a hard carry and feel like he will be focused, the Divine Shield  is nice, otherwise  the  Divine Storm  is a really good ult which offer you a lot of cc, especially combined with  Benediction  at 16 (which gives you 2  Hammer of Justice  in a row).