What if we made so each shield-line Gambit exclusively emphasized one thing, and did that one thing very well. Dance of War and Conviction for their respective mitigations (and the heal from Conviction), Readied Blade for Parry, Shield Up for Block, Shield Mastery for Evade, Shield Tactics for -incoming Tactical Damage (and CC immunity), Impressive Flourish for -incoming melee damage, Maddening Strike for -incoming Ranged Damage. This is just a rough idea, but the advantage to consolidating the effects would be to allow you to pick only what you need, rather than having to maintain 11 gambits (all of the above, plus three HoTs) for optimal survivability.

If you are running into a hoard of Orcs, you pop Shield Up, Shield Mastery, and Dance of War on your way to them, Open with Readied Blade, and Impressive Flourish, and BAM: you have everything you need against a blob of melee Orcs with only 5 gambits. Grabbing the other defensive Gambits really won't do anything for you, except for the Conviction heal, maybe. I suppose technically this would be 8 Gambits counting your self-heals, possibly still more if it's a large pool and your leaches are useful, but it's still an improvement by several gambits over the current system where you need to try to maintain at least 11 Gambits to be at full capacity.

Another advantage of this system is you could decide with slightly better clarity what you needed, and reach full capacity quicker in that area. Dragon just come out of a phase-change? About to nuke you with Fire? A quick Shield Tactics is the best response here. Tons of Lizards just join the fight? Getting all of your Evade at once is probably better than mitigation is this instance, so pop Shield Mastery. Other things can come later.

Unless you're really in an encounter with 1) a lot of enemies, 2) every type of damage happening at once, including physical, tactical, and ranged, 3) an encounter in which BPE and mitigations are equally valuable, this system would offer a small improvement both in quality of life, keeping the number of buffs we have to maintain slightly lower and allowing you to react to changing situations or phase-changes in a slightly more decisive manner. This would also help balance the gambits, as I noticed last Bullroarer that I constantly reached for Shield Up, but Shield Mastery came much later in my rotation as it simply wasn't as useful.

It's a small change, but I think it would offer moderate improvement as well as falling in line with OnnMacmahals vision of the gambits only doing 1, or maybe 2, things.