I was on your side until about 4.2. I think a lot of people were. But then there was this big push from WAR mains to change Shake it off, which came at the expense of fixing DRK or even acknowledging that it was in a bad spot. Now you're doing it with Onslaught.
Other people are entitled to have an opinion of your conduct. Shame is an important self-regulator. It keeps you from being reprehensible and selfish. And if you don't have that self-regulation, then please allow the rest of us to assist you with this. The devs are clearly prioritising WAR issues at the expense of everyone else, so let's break this cycle from both ends. The hostility isn't just from me. Look around on the forums and on reddit. People are tired of this six year long favouritism. Even SCH didn't keep it up for this long.
Xeno is the one who has mentioned removing the rage cost on Onslaught. But it's also worth noting that he's the one who felt that Direct Hit and Crit made WAR dps optimisation too difficult, which is why a lot of things on WAR do both now. So this isn't about what is balanced so much as what is good for WAR.
If Onslaught was identical to the other tank gap closers, it would be flat out worse. The charge system doesn't give you two charges every 30 seconds. It just lets you hold one in reserve. So WAR still has the highest mobility out of any tank (double the mobility, in fact). The only difference is that outside of certain circumstances that grant a free Onslaught, it's designed to be a dps neutral mobility tool, rather than an oGCD potency gain.
So take your pick. Do you want double the mobility? Or do you want the removal of the gauge cost. Either is fine. Keep it as it is, with half the recast of the other tanks, or change it to be identical to the other tanks. What I don't want to see happen is for you to get the recast cost removed while keeping a 15s recast, and get yet another clear cut advantage over the other tanks.
I know it's kind of inevitable (this sort of decision-making always happens with the devs, as far as WAR is concerned), but I do think that the rest of us have the right to call you out on it.
That's pretty much all that needs to be said here.