I think you should move the small skulls away from the edge a bit where possible, they're uncomfortably close to it. The distance between the skulls and edges is also inconsistent, it's 2 in some places, 3 in others. Make it 3 everywhere. In general, you want there to be more space between the pips and the edge than there is between the pips on the 6 face.
The skull-edge distance is more obvious than the skull-skull distances because there's more contrast, so I'd sacrifice consistency in the latter for the sake of the former. You could keep the distances between the bottom-most skulls and the edge 2 so that the 6 face looks good and the rest stay consistent with that. Since the teeth aren't solid red, it still looks alright.
Here's an edit with the spacing I suggested:
I also edited the skulls on the 3-6 faces to be more consistent and tweaked the eyes. The 6 face has some alternate eye ideas for you. In all cases the eyes are a pixel higher, because I think that reads as more skull-like than having the eyes almost in line with the nose-hole.
For what it's worth, most tabletop gaming dice have digits rather than arrangements of pips, since players often need to match them up to damage tables and perform math on them. For that, digits take out the extra conversion step. Pips are appropriate for games with less post-roll math, such as games where you're just looking at the total number of pips on 1-2 dice or looking for matches, which are easier to spot with arrangements of pips than with digits.
That doesn't necessarily mean you should change to digits, just that you should think about what purpose the dice serve. Since the computer does all the lookups and math for the player, the on-screen dice are probably purely decorative, in which case go for what looks better - which is probably your skull-pips.
Gameplay feedback, feel free to disregard as I am not a Warhammer player:
I like the idea of mutual damage and of grazing damage, but I feel like that would work better with higher health amounts. When even your "tanky" characters have only 5 health (that's as much as your UI will fit!), it does mean constant healing, and it means that any attack that does more than 2 damage (i.e. a not-grazing attack) is very powerful. Plus, it means there's not a lot of difference between your tanks and non-tanks, health-wise. If health can go higher, then damage amounts can be more nuanced and varied. If you do damage in half-hearts, you can fit 10 health points in the same space, and therefore have more variety in health between classes. If you do segmented bars, you can have even more.
If each point of health is less critical, then players can risk taking a bit more damage to focus on dealing damage, instead of having half their party be healers. You don't want too much health though - every point should matter! I think 1~10 is a good amount (5 hearts with half-heart as the minimum damage). The base damage for attacks could be in terms of full hearts, possibly reduced to some number of half-hearts by defensive gear and spells.
For energy management being important, card games like Magic and Hearthstone are a good reference. In those, you don't get all your energy to start with, it builds up, and you can choose whether to spend it on one big boom or several smaller things. If your game only allows one combat action per turn, you can still get this sort of management by having energy carry over between turns and regenerate slowly (e.g. one bolt or one half-bolt per turn). Having (slow) energy regeneration turns time into a resource that players can manage, and it means that if you have energy-replenishing items, they can be very rare and valuable, useful only for emergencies.
As with health, I think energy would be more fun if it can have a little more variance than just 1-5.
Edit: Consider attacks, including ranged ones, with knockback. If movement ranges are small and positioning matters, forcing a change in position can be very useful.
Also, facing direction should probably matter. Gear should add different protection from different directions. For example, shields would probably offer no protection from the back or the sides while having good front protection and a chance to completely block an attack, while armour would offer some from all directions, but with no block chance.
I feel that many games with facing mechanics don't take them far enough - there is usually very little opportunity to end up facing away from an enemy, since your party and the enemy party usually start in different locations. Consider passive and active abilities that work with "suboptimal" facing - for example, an ability that grants a once-per-battle defence bonus against backstabbing, or a magic ability that does more damage to enemies the caster is facing away from.
Another way to get around facing being a bit useless is to make it harder to change direction. FFT let you set your facing at the end of each character's turn, no matter what you did during the turn, so of course you'd always face the enemy, and that step was tedious. But what if you were stuck facing whatever direction you turned to face while performing an attack or ability? Suddenly, healing and melee AoE spinning attacks turn risky!