Build is fine. Going 18/18 is a fine build for 1h+shield. Maybe next gen try 21/15 if you prefer swords and have trouble with glancing blows.
Constantly switching armor can be confusing, because you constantly change movement speed and infuence your effective wpf. Try making one loadout you can afford all the time. Maybe save up a bit if you don't have enough 'buffer'.
Scimitar is a fine weapon, but hard to use against heavier armor. Avoid those guys. If you can't, go for headshots and make sure you hit with the 'sweet spot' of your weapon (at the maximum range of your swings). Holding attacks can also help prevent glancing, but not many fights let you hold attacks. So go for headshots and use overheads a lot. And use an occasional feint against good blockers.
About enemies being able to get another swing in after you block: it's about timing and footwork. Only solution is to practice. A friend of mine that recently started was helped by the realization that you do not need to wait 'till you hear the hitsound on your shield.
About bucklers in battle mode. Don't. Get a proper shield instead, bucklers are great for duels but not that great in battle mode. You'll get shot a lot.
