As I've always been in favor of large shields because they look damn cool and are +- the equivalent of being a tank, I believe it's long overdue that large shields recieve a buff. They are currently outclassed by small shields because small shields provide more abilities (especially the counter skills) and have similar stats.

My suggestion of reworking the large shield are the following:

- As you need to have Shield Mastery at Rank A and level 60+ to unlock wearing large shields, Large Shield Mastery should recieve a passive bonus to survivability.

My suggestion is to include a passive damage reduction ability of 2% per skill rank, maxing out at 20% damage reduction at Rank 6.

Additionally, this damage reduction doubles to 40% while rolling over the floor to cover the weakness of Fiona not having an I-frame on her dodge, simply because while rolling, most of her body is covered by the large shield (in contrast to standing), and from Rank 9 onwards you have a certain chance to block an incoming attack while rolling.

- Increasing the maximum rank of Iron Defence to 6.

Iron Defence is the only Large Shield skill at the moment, and it's pretty pathetic, considering the duration to CD ratio.
I'd like to see it cap damage reduction at Rank A at 75% and instead have more CD time reduction from Rank 9 onwards so you have a ~ 50% uptime ratio.

Also, the skill should have a similar option to Shield Enhancement, so that the buff duration increases every time you actually block an incoming attack (e.g. 2 seconds on normal guard/heavy stander and 4 seconds on perfect guard/heavy stander at Rank 6 [0,5 seconds increase from Rank 9 onwards to have 2 seconds at Rank 6]) so you actually still have a reason to block attacks while Iron Defence is active.

- boost large shield stats

Currently, large shields don't have much more additional stats compared to small shields. This should change so that large shields provide more stats compared to small shields, especially STR and WIL.

- add a new large shield only passive skill,called "Bulwark".

Similar to how small shields have the ability to counter attacks, large shields should have a useful ability.

Bulwark allows you to deal damage to the enemy by blocking its attacks with your sturdy and pointed/sharp shield. Most of the large shields have some sharp edges/horns/spikes, so why not utilize this to deal damage to the enemy while blocking?
The damage should depend on the defence of your shield, and every block will deal a certain percent of that defence as damage.
Perfect Guard/Heavy Stander will deal enhanced Bulwark damage. This should give more incentive to block attacks rather than just tank them face on,even if interrupting your combo.

Also, this skill will allow you to go from Guard into Heavy Stander from rank 9 onwards by holding down the guard button (default = space) for a longer time period (e.g. 1-2 seconds) to make it easier to turtle with your large shield[which is the purpose of the large shield anyway).

- Perfect Guard with a large shield will now allow you to chain into Beetle Crusher

As the large shield provides enough covering area, Beetle Crusher is the best ability to prepare while guarding/blocking an opponents attack.
while you keep your shield up, you can swing back your hammer and prepare the overhead swing attack just fine, so why not allow this attack to combo with guarding?

With both a chainable Beetle Crusher and the damage reflecting skill Bulwark, large shields should be able to cover the damage disparity between Hammer&Sword and/or Small Sield&Large Shield, while keeping the focus of Large Shield mainly on defence and damage mitigation & awarding blocking in a similar war to how Small Shield+Long Sword does.