I play shout healer tank warrior and it works great in PvP and PvE
I thing though, I would take out on my mark, it only targets 1 person and you could get a little more CC in, so I suggest using fear me. It's kind of like a better stomp that can heal
I think you're right on On My Mark unless I'm playing with a specific team and we have synergy. For the most part, I will be using Fear.
Warrior shout builds are not as effective in pvp as pve/wvw. Banners are great in team fights but they're too situational with the positioning requirements and long cooldowns. Shouts increase in effectiveness for each player you can heal, so it can be nice in an organised team. Personally right now heavy CC is the crux of a support warrior keeping faces in the dirt. But hell I use an unorthodox build that works for me so wouldn't give up on it yet.
I'd run rune of the soldier for condi removal, i'd suggest something else instead of great fortitude and als picking up shield mastery. Finally be disciplined in your battle standard usage, try dropping it when you have an ally or two in downed state to give an instant res and flip the table on the enemy otherwise just dropping it as soon as you see an enemy is a huge waste.
After playing with the build more last night, I understand what you're saying - Shouts aren't as effective in PvP, especially if built around the idea of healing from them. I will fiddle around with the runes you suggested. And, with the Banner, I never drop it unless there are one or two downed allies, it would be a huge waste with its massive cooldown to blow it without any revive occuring.
Thank you for the feedback. I'll continue playing around with the build to see whether or not it'll suit me. It looks like I may just want to roll a Guardian and look into making a support spec on that class.