R2 - Repair Drone
Reduce the cooldown of Guardian Shell by
30 seconds. Increase the duration of Guardian Shell's Unkillable by
1 second and allied Heroes affected by Guardian Shell gains a Repair Drone for
8 seconds which heals them for
2.5% of their maximum Health every
0.5 seconds.
Active - Templar's Pledge
Cooldown:
30 seconds
Activate to reset the cooldown of Unity Barrier. If Unity Barrier is cast within
1.5 seconds of resetting it, grant an additional Shield equal to
8% of allied Heroes' maximum Health. Basic Attacks reduce this cooldown by
0.125 seconds, doubled against Heroes.
Active - Reclamation
Cooldown:
60 seconds
Target an enemy Fort or Keep to temporarily make it target enemies instead, prioritizing Heroes, for
18 seconds. While active, the Fort or Keep gain a Shield equal to
20% of its maximum Health and has a
30% increased Attack Speed and Range. Can target enemy Catapults and Mercenaries, converting them to Karax's side permanently. If used this way, refund
50% of this ability's cooldown.
Active - Purifier Protocol
Cooldown:
90 seconds
Activate while dead to consume
100 Solarite to instantly respawn in your previous location, gaining
40% Movement Speed for
6 seconds. During this time, Karax's ability recharges
100% faster. Allied Heroes in Karax's Power Field have their Basic Abilities recharge
75% faster.
Generally speaking, I think it's good that the three abilities cover different aspects. Offense, Defence, and Utility. A concept like this runs the risk of having players conscript to either spreading things evenly, or just going all-in, when what this moveset wants is to encourage diversity.
In terms of the details, however...
Q: Pretty basic, but when you think about it, it's really just Zarya's projectile, but with a fixed travel time. There's room for overlap, but as history has shown us it can be difficult to make impactful talent options for moves with multiple charges without them becoming too strong. Perhaps it'd work better firing all four shots at once in some way?
W: Basic but effective. That said, I'd remove the line about granting 5% extra per ally. It does need something to make it distinct from Tyrael, but I think A) Karax is a quester, he shouldn't be rewarded for always being near his team and B) The upgrade system should be where the extra power comes from. Maybe to make it more distinct, it could be a castable AoE that grants shields to everyone in its radius.
E: Is... just not the kind of move that should be in Heroes of the Storm, sorry. Passive Mana regeneration, while innocuous, destroy's the game's "war of attrition" aspect, as mana is an element that really helps to break stalemates. Malfurion's is very limited (and arguably shouldn't be in the game either), Ana's is a heroic, and Probius gets it only as a very late-game option. Though more problematic is that you've given cooldown reductions as a baseline ability, which is incredibly powerful, but also not that fun to use when it's just a "press this button and your team goes nuts". Ana and Malfurion have the benefit of needing to pick a specific target, which isn't much skill expression, but it's enough to matter in those critical moments. When it's just to your entire team, it's just "press button, watch everyone else have fun". Yes, the timing can be critical, but the effect is non-specific enough that there's no amount of balancing that can be done to make it both fair and fun at the same time. Remember, you're balancing against Nano Boost, here. This is the only ability I'd say should be completely redone. Maybe it could live on rebalanced as a heroic, though, as R2 is a little basic. Perhaps you could even have it be an aimed thing, where you create a moving area that lowers the cooldowns of allies inside it, so you get to dictate where your entire team stands (and if you make a bad call on when to go in, you effectively waste it as it travels along without the team).
However, the strengths and weaknesses of those abilities aside, I think the trait needs some serious adjustments.
To start with: The 60 second cooldown completely kneecaps Karax's fun factor. A questing hero's goal should be to become above curve, to have something to show for their antics when the chips are down. Azmodan, Nazeebo, and Zul'jin are rewarded for playing well by becoming more powerful than they should be for the level they're at, while Karax... can only be judged against if he's managed to activate his trait every minute on the minute. So... scrap that entirely, or give it a more reasonable 10 second cooldown. Now Karax isn't just trying to hit his quota, he's trying to get ahead of the game. From there, the rate and reward of Solarite becomes the focus.
On that note, though, I think the way he's rewarded is a bit off. For starters, due to the inconsistent nature of objectives, that simply can't be where he gets Solarite (and the same could be said of camps, since Blackheart's would make him absurd). There's also the issue that takedown based rewards can become snowbally, and are similarly inconsistent. Sometimes you get games where there are only 9 takedowns all game, sometimes you get ones where there are over 50, which is why takedown-based rewards have to be measured carefully. I imagine these inconsistencies might be a part of why you added the cooldown. But I think, vaguely speaking, the means of earning Solarite could be handled like Azmodan, with one main way of collecting it, along with a second way that's set by your level 1 talent (basic attacks against heroes, landing abilities, regen globes, minions kills, and yes, takedowns). This creates a level of consistency where the player can choose the option that best suits the map and enemies. If it's a low takedown map, then regen globes it is. It creates fewer situations where the player loses right at the starting line.
Oh, and making minions grant Solarite randomly is naturally not a great move. If it is going to be tied to minion deaths, either make each drop 1 and increase the Solarite required to level up abilities, or make it come from every third minion kill.
Normally I don't go into talents that much unless I'm looking for specific role-related holes, but here I think you missed out on something key: There should be some quest talents that grant a reward for upgrading abilities. Now, I wouldn't say that there should be a strict "once you upgrade Q 5 times, it can now X" (which would be a bit crazy and encourage people to put all their eggs into one basket... unless X was "lower the cooldown of W and E" or some variation), but some goals to strive for would be appreciated. Perhaps something like "Every X times an ability is upgraded, its cooldown is reduced by 1 second, up to 3 seconds.", which does have the opposite problem, but players may still elect to upgrade only two of the abilities.
(Also Solar Core is completely busted as you can just stack them behind your core for infinite free Solarite forever at no risk, and the damage generated isn't really a deterrent to that. It just has no counterplay as-is and isn't very interactive.)
Also I'd say something about Temporal Field but I'm still not sure how I feel about slowing cooldown reductions in general. It's either a dud design space, or an untapped one.
Overall I'd say you're on the right track, you just need to find that quintessential factor that rewards the character for weighing their options and picking the right one, and I think Talents that generate or reward solarite is the right way to go.