I have so many criticisms about these icons, mostly about how much of them do a horrible job of matching their graphic information to the skills they are suppose to represent.
Like the puppet skills that use chains in place of strings. Or that Way of the Gun is some random buff man that could easily represent the skill Berserk. Shooting rush could be mistaken for charging strike. Flash launcher could be mistaken for an archery skill because it's an arrow tip. Evasion doesn't look like evasion, since its just a foot and not clearly showing any acts of evasion. Dual gun mastery only shows one gun in the icon.
I also criticize that none of the skillsets are not categorized by the colors that the default icons the game paints them with. This means that it'll take even longer for the player to recognize the icons when they need to use skills, since the icon colors makes the skills distinctive on what type they are. Like magic skills are blue, warrior skills are red, life skills are yellow and so on.
The skill icons in the vanilla game are all results from careful conscious design decisions that makes each and every skill recognizable as well as easy to read and reasonable to compare to the actual skill. There are more to icons than just highly detailed and edgy pictures. And it is the responsibility of the person designing these HD icons to enhance the player's gameplay through improved graphical UI, instead of confusing and harming it.