The WPF drop is so significant that you are literally hitting at half speed
This is true to a point, but isn't the whole story. It may be true in that, assuming the ABSOLUTE heaviest gear (27.9 body, 4 helmet, 3.8 boots, 2 gloves) in all categories you will go down from 111 base no WM level 30 to 66 wpf; you will have a little more than half of your written proficiency and suffer the additional malus to to speed and damage, but these, and especially speed, are minor losses. 100 wpf will increase your weapon speed by like 1-2% if I'm not mistaken, so you're missing out on like, .5-1% additional speed- extremely minor, your base weapon speed has basically all of the impact on your swings.
As a guy who moves very slow myself, trust me, it is balanced.
The problem here is that heavy armor becomes most overpowered when coupled with Strength builds (for the sake of argument, 27/12 or greater) who
already are quite to extremely slow
with or without the armor, and are thus affected by the penalty to movement speed much, much less harshly than someone with higher agility/athletics wearing the same armor while at the same time gaining a greater boon from its use due to higher health values with or without Ironflesh. Basically, if you're playing a low agility/athletics character, you may as well wear heavy armor if you're not going to wear a gear set under the threshold at which it begins affecting movement.
And yes, charge damage was finally adjusted some and an anti-cav siege item was added, they were both a long time coming like a lot of the adjustments to items we're seeing occur.