I've gotten most of the way through the game while wearing some leather armor I got in basically the beginning of the game. The red-eyed skeletons hit for about a third of my health.
 
I got some better stuff, but it was too heavy, which meant dodging was impaired. But I need to dodge, that's what I do to not die :( 
Maybe the defense bonus makes up for it? Nope, the red-eyed skeletons still hit me for about a third of my health.
 
Then I fought the Old King miniboss in 1-1, and got a full new armorset from him that was even better.
I moved even slower, but the red-eyed skeletons still hit me for about a third of my health.
 
Then Biorr died at the dragon in 1-4 and I got his armor.
My movement slowed down to a crawl, I couldn't run and dodging was completely out of the question.
The red-eyed skeletons STILLLLLL hit me for about a third of my health.
 
Solike...why's that even there? I figured there's a specific stat maybe tied to your ability to handle heavy armor, but I'm stii unable to wear a goddamn steel helmet without automatically being unable to dodge.

There's a ring you can receive that'll give you great agility even while wearing the heaviest of armours. In general, though, the heavy armour just looks cool. The main reason why I wore it with my Priest.

One of the stats determines how your move in heavy armor. 
Raise that stat any you'll be able to move in it like any other piece of armor.

" @Ventilaator:  If you stay below a certain percentage of your carry weight you can still dodge, or run.  "

" @owl_of_minerva said:

" @Ventilaator:  If you stay below a certain percentage of your carry weight you can still dodge, or run.  "

I specifically tried this by giving everything I was carrying to mr Thomas and trying to equip the tower shield.  Dodging still sucked. "

It's all to do with stats and how you build your character. If you put a ton of points into magic and speed based skills then the heavy armour will do nothing for you. However if your build your character's strength and endurance up then he can wield the biggest weapons and move around easily in the heaviest armours. It's common sense really :|

The tower shield is very bad. Sure it got great damage reduction, 100% normal/ 60% magic/ 90% fire and awesome guard break reduction but it's so heavy. It's better to use a Purple Flame Shield. It only has 30% magic damage reduction and the guard break reduction is a bit lower but it's much lighter. It only weighs 8 instead of the tower shields 30! The purple flame shield is also much easier to upgrade since it doesn't require colourless demon's souls. If you're fighting a lot of magic users then you should use the Dark silver shield since it has good stats and 100% magic damage reduction.
 
Edit: A fully upgraded Purple flame shield has 82 guard break reduction vs the fully upgraded tower shields 85.

" It's all to do with stats and how you build your character. If you put a ton of points into magic and speed based skills then the heavy armour will do nothing for you. However if your build your character's strength and endurance up then he can wield the biggest weapons and move around easily in the heaviest armours. It's common sense really :| "

" @Raymayne said:

" It's all to do with stats and how you build your character. If you put a ton of points into magic and speed based skills then the heavy armour will do nothing for you. However if your build your character's strength and endurance up then he can wield the biggest weapons and move around easily in the heaviest armours. It's common sense really :| "

I figured as much, and have been increasing my strength and endurance, but still, whenever I try to equip anything that is not the current leather armor set I have, it automatically makes the dodging super slow "

" @Raymayne said:

" It's all to do with stats and how you build your character. If you put a ton of points into magic and speed based skills then the heavy armour will do nothing for you. However if your build your character's strength and endurance up then he can wield the biggest weapons and move around easily in the heaviest armours. It's common sense really :| "

I figured as much, and have been increasing my strength and endurance, but still, whenever I try to equip anything that is not the current leather armor set I have, it automatically makes the dodging super slow "

" @Ventilaator said:

" @Raymayne said:

" It's all to do with stats and how you build your character. If you put a ton of points into magic and speed based skills then the heavy armour will do nothing for you. However if your build your character's strength and endurance up then he can wield the biggest weapons and move around easily in the heaviest armours. It's common sense really :| "

I figured as much, and have been increasing my strength and endurance, but still, whenever I try to equip anything that is not the current leather armor set I have, it automatically makes the dodging super slow "

You can always check the stat screen to see your maximum equipment burden, and how much what you're currently rolling with weighs. "

" Is the number the specific number I should keep my stuff below if I want to dodge quickly? "

Biorr doesn't drop the ring you find it in the 1-1 dragon area.  Purple flame shield is crap, the brushwood shield has superior fire cut and matches it in all other aspects for only a minor stat/weight gain while the steel shield matches it 100% except you lose fire cut but weighs less and takes less str to use.  None of them can parry though so eh.  There are reasons for using heavy armor though, for example, the high fire resistance of the brushwood set helps alot against this one flamelurker guy...

" Biorr doesn't drop the ring you find it in the 1-1 dragon area.  Purple flame shield is crap, the brushwood shield has superior fire cut and matches it in all other aspects for only a minor stat/weight gain while the steel shield matches it 100% except you lose fire cut but weighs less and takes less str to use.  None of them can parry though so eh.  There are reasons for using heavy armor though, for example, the high fire resistance of the brushwood set helps alot against this one flamelurker guy... "

"One of the stats determines how your move in heavy armor. Raise that stat any you'll be able to move in it like any other piece of armor. "

" Biorr doesn't drop the ring you find it in the 1-1 dragon area.  Purple flame shield is crap, the brushwood shield has superior fire cut and matches it in all other aspects for only a minor stat/weight gain while the steel shield matches it 100% except you lose fire cut but weighs less and takes less str to use.  None of them can parry though so eh.  There are reasons for using heavy armor though, for example, the high fire resistance of the brushwood set helps alot against this one flamelurker guy... "

" Brushwood shield requires colorless demon's souls for upgrades and the Purple flame shield has higher guard break reduction when it's fully upgraded and it only needs hardstones. The purple flame shield is much better IMO. "

1. Biorr does drop the Ring of Great Strength, see here.
2. The Purple Flame Shield does not take more stones to upgrade than the Steel Shield.