DnD Next is having a bit of a thing with armour. There is always a real struggle to sort out how armour should work and the stakes are relatively high because if you get it wrong the world doesn't make any sense. Sometimes that is because everybody runs around effortlessly performing athletic maneuvers in full plate armour (DnD 4th), sometimes it is because nobody should wear armour (World of Darkness), sometimes it is because armour makes you invulnerable (Cyberpunk).
The current direction Next is going seems to be to improve heavy armour. This is a good thing because up to this point they have given heavy armour a very high AC bonus but serious drawbacks including no Dexterity bonus to AC, slow movement, and a big stealth penalty. Those added up to a situation where people using Strength based builds with heavy armour were fine at melee but awful overall since they lacked mobility, ranged capability, and stealth. The recent innovation is to allow people with high Strength to ignore armour's speed penalty which is a fine start but does not solve the problem.
The fundamental issue is that Dexterity is awesome for everything and Strength is awesome for only one thing so Strength builds are just going to be bad. Unless they make Strength builds way better at melee combat (which is a terrible decision!) there isn't a good way out of this mess. RPGs have a history of making Dexterity good for everything from initiative to avoidance to ranged weapons to finesse weapons and then wondering why everybody only cares about Dexterity. There are a lot of ways to reduce the current overpowered status of Dexterity like shifting attack bonuses to Dexterity but damage bonuses to Strength, making initiative based on Intelligence, or making less spells require Dexterity saves. Without doing some of these things there is no good way to make the system work.
In Heroes By Trade I really want heavy armour to be excellent for stand and fight battlefield conditions but poor for the usual swimming, climbing, sneaking, and running that adventurers generally face. At the moment characters have a base Speed of 5 and armour reduces that by 1, 2, or 3 depending on if it is leather, chain, or plate and increases their damage reduction by the same amount. Generally people have opted for leather armour or none at all and that seems to be working well. I really want an average guard at the gate or infantry fighter to say "Yes PLEASE" to plate armour but dungeon delvers who explore far places to say "Meh, no thanks. I might have to run away."
The trouble is that I can quite decide how to implement the penalties to athletic maneuvers that would make sense with heavy armour. I feel like Hiding, Sneaking, Athletics, and Acrobatics should be penalized but so far keeping track of all the possible bonuses and penalties to various skills has been challenging for my playtest groups and I am sure that the armour penalties have been forgotten. Although HBT is drastically simpler in this regard than DnD is the system is different and therefore takes some getting used to. At the moment the penalties to skills are the same as the Speed penalty above (1,2,3) so swimming in full plate is quite feasible. I keep thinking that maybe I should ratchet those up to (3,6,9) to emphasize that heavy armour is not fun to run around in. I don't think that those penalties need to be there from a balance perspective but I do feel like they should exist from a immersion perspective.