It's very confusing to compare ShO/Grit and IB since the only crossover between them is the 20% damage reduction, and even that has a difference in that IB only lasts 6s and ShO/Grit can last as long as you keep them on for. It then gets even more confusing when you start considering that you need to be in Defiance to use IB and Defiance is a more direct parallel to ShO/Grit.

A potentially better way to put it would be saying that you currently only go into your tanking stance for aggro (which isn't even necessary if you have a WAR and he pulls) as the damage reduction isn't necessary especially when it costs a large chunk of your DPS, which is king in XIV.

Anyway, to keep things on topic I'd recommend just not raiding. I know that seems blunt and probably pretty weird since you clearly care about DPS and are therefore more competent than the majority playerbase, but the thing that leads me to that statement is this:

Our static is kinda made up of folks who can't really fit regular raiding into their schedule, so our group comp is a little off, but I'm curious.
I imagine you're in a bit of a forced hand situation - you want to raid, but due to your schedule you're stuck with this really poorly constructed group. You care about your DPS and helping the group, but the healers don't want you out of tank stance, you don't have a NIN, you don't have a WAR, and the BLM won't get Quelling. So essentially you're left with 3 realistic options:

1. Level WAR and switch mains, letting you focus more on DPS as well as benefiting the group by applying Storm's Eye (and Storm's Path as necessary). I imagine you like PLD, or perhaps you don't have enough time in the day to level a whole new class, but realistically this is the only way to fix your group comp as-is and improve your overall experience.

2. Quit raiding. Let's be realistic here, if you care about working as a team and upping your group's potential while improving yourself and the rest of your team just kind of "shows up" then you're a bad match for eachother. I have been a part of a few raid groups with conflicting interests, and all of them fell apart because of it. Quitting all together and finding another game to play, or picking up a new hobby, will probably lead to a lot more fun.

3. Stop caring about DPS. Just do what they do and show up. Make friends with your other raid buddies and try to make the atmosphere relaxing and enjoyable. Maybe, eventually, this will lead to them thinking that working as a team is productive and more satisfying, though that's unlikely to click for awhile.

I realize you are one of the relative few who actually cares about his performance in the group and helping the group as a whole, but based on your circumstances these are the only options I see working out positively. Your slight increase to Shield Oath DPS is essentially a drop in the water. Your heart is in the right place, but your group is holding you back, and due to your scheduling I imagine you're not going to be able to find a group that has the same mentality as you.

But who knows I could be off the mark entirely. If you're having fun either way, then I'd recommend just not really caring about your DPS to an optimized level as being stuck in ShO will kill all the optimizations you make.