Used it for a bit. The pacing of the rate at which this growth seems appropriate for it to be a viable, unique, and still niche (ie., not overpowered) trait for this class to have - the trait only applies to the hero itself, and the best multiplier Talent the hero has is Bloodthirsty (no Fireblade, no Hunt). Being restricted to red weapons is very limiting and there is a lot of counterplay. The problem with most stuff that gives stat growth is that it doesn’t grow at a fast enough rate to really be a viable consistent strategy versus stuff at slightly above your total strength, let alone “upscaling” into stuff with 2-3 times your stats (I’ve found that beyond that, you basically just use Manglikes and/or stuff that scales with your own stats that can get a large boost). In using a pure skull spam double converter team in explore 12 with this class, I found my attack grew about as fast as with Warlord or Dervish as with the “bugged” Barbarian trait, and either arguably has better tools for skull setups and aren’t restricted to a single color.
Note that 3 attack every gem match of any color is nearly functionally equivalent in most fights to 3 attack every 4 or 5 gem match unless your team is dropping the turn constantly (worse if half your matches are skulls, because the trait doesn’t trigger on skull matches), and if you are, well, your hero isn’t going to last very long in any mode with the tools we have (we have root trap stall and agile, but this is otherwise very unsafe compared to its general skull damage output). Keep in mind the tools that are in the game now - the manglikes, the skull strikers that can occasionally just kill outright with very minimal setup (Webspinner, Umenath, TINA, even low rarties like Savage Hunter or Tracker). 80+ attack is very easy to get, as is the ability to one-shot with skulls.
Relegating the trait to only grow attack when matching reds and only on the hero pidgeonholes it into a much tighter category, likely with only Gar’Nok if you want to make effective use of this (so you’d grow 6 attack every Gar’Nok cast, you’d get off 3-4 and gain like 18-24 attack, then die because the spawn streak breaker code said no and nothing about your setup really protects you from the enemy team taking all that mana). No Fire tree also means you are unlikely to fit a firestorm into your build, so your Lightning Strike can’t really even help a ton with that without a very specific setup that is likely way more trouble than it is worth (considering the aforementioned alternatives).
The potential of the Forest and Storm trees keeps this class being usable even with the “intended” trait, but in ways where I’ll likely never make use of the trait. When stuff is going to be weak, it really bothers me when it can’t be made to have synergy, because then I see the potential cap out early (at lower than the tools already available) and then I’m already bored with it. If the trait does get changed off the current version, I really hope it can at least have some synergy potential added to it. “All orcs gain 3 attack when matching red gems” or, more appropriately, “all orcs gain 3 attack, life, and armor while matching red gems” would give it some, albeit limited, synergy unless orcs receive some kind of relevant buff that completely changes their design (which is unlikely). It would at least be something to play around with.
tl;dr: Don’t nerf the trait, but if you do nerf the trait, at least redesign it to have an appropriate synergy.