Basic change would be go a bit more STR heavy since:
Less room in many more places for using speed bonuses to compete with PS.
Shoves OP in any scenes with tall ledges, which are more common in siege.
Chasing ranged isn't needed.
Generally, I'm a bit against using IF since non-glancing hits generally do at least 15-20 damage, so higher IF values generally just yield more situations where you can take that one extra hit vs the IF just doing nothing. However, getting hit one more time before dying/killing in one less hit gets more important with downtime from respawning/running back to position as a factor for winning. Plus in siege there's generally less cav bumps instakilling black barred people, so the only concern is weak spammy archers.
Level 34 (80 873 140 xp)
Strength: 24
Agility: 21
Hit points: 59
Power Strike: 8
Athletics: 7
Weapon Master: 7
1h or pole primary Ironflesh: 0
Shield: 1 -> 4 -> 7
2h or pole primary Ironflesh: 0 -> 3 -> 6
Shield: 1 -> 1 -> 1
Any primary Ironflesh: 0 -> 0 -> 3
Shield: 1 -> 4 -> 4
Chosen primary weapon : 170 wpf
While you only have 1 shield skill:
Grab Leather Covered Round Shield if crossbowmen are around. If it's +3 then even +3 arbs with +3 steel bolts shouldn't be able to penetrate it without crazy speed bonuses, plus it can provide a hefty back armor bonus.
Otherwise grab Old Board Shield for dealing with arrows/thrown since it protects feet even with poor investment.