Instead of dealing a set amount of damage, brain rupture now kills the enemy instantly (excluding monstrosities), but takes longer in proportion to the enemies health, minimum charge time 1 sec, on horde and shooter enemies, max charge time 5 seconds, on crushers and bulwarks. all status effects that increase the damage dealt by you, or the damage taken by enemies reduce the minimum and maximum charge times.
Alt fire will now charge at half the rate, so to charge enough meter to kill a crusher you will need to charge for 10 seconds.
I like the idea that it 1 taps enemies and that the charge time gets reduced if the enemy is already low, or takes damage while charging.
Taking 2x the time to cast, seems far too long. Unless all targeted casts are very fast.
I have four options for right click precharging (option 4 is my favorite):
A simple precharge at slightly reduced rate. If you have precharged long enough for the target that you pick by left clicking, the attack will go off instantly. If you have not precharged for long enough, the remaining charge time has to go through, first. (this is probably what you meant, but i think 2x charge time is far too long)
A relatively fast precharge (fixed damage) that just deals enough damage to 1 shot weak elites and specials (basically as much dmg as it deals now). You can still attack stronger enemies with it, but they will not get oneshot at full hp.
A slower precharge (fixed damage) that always takes as long as an aimed cast against full hp crushers and always deals as much dmg as a regular cast against full hp crushers (independent of the target that you cast it on).
A cast that can be charged as short or as long as you want to, building up more damage the longer you charge it. By left clicking a target, you can apply the damage at any time. It deals damage and may or may not kill the target, depending on your charge time.
This would allow you to do funny things to bosses (like 1 shot a demonhost, if you precharge for like 2 minutes with Empowered Psionics), while also enabling you to do the things that the options above can do, if you know how long you have to precharge in order to meet the damage thresholds for the enemies you want to 1 shot with a precharge of minimum duration.
I think that having the option to do relatively quick casts is important, since Brain Rupture hits also stagger enemies.
With quick casts, you would be able to stop a dog/bomber/burster/trapper, stagger berserkers, save teammates from overheads, or open bulwarks quickly.
This is actually a really good idea, definitely would need to tweak numbers around to what feels right, but it would be much better than brain rupturing the same damn target 3 times in a row. Regardless of if breakpoints were tweaked, it makes no sense to have to rupture a targets brain multiple times to kill it