It seems that in my hands rainbow gun is a lot more profitable than magnet sphere in all cases, where it is more than 1 enemy.
Theory:
Calculations: magnet sphere exists for 7 seconds an hits at a rate equal to use time of 9 (6,6 times/sec)
In my set it does 95 dmg and 30% crit
Result – 805 DPS
Total damage dealt – 805*7 = 5635 damage
Rainbow gun: 89 damage in my case, 30% crit, hits enemy 5 times/sec, lasts for 20 seconds infinite pierces (most important)
Calculations: 1 enemy – 89*5*1,3 = 578,5 dps
But, at events (for what it was designed) there are at least more than 3 enemies, which results in >1700 dps
So, total damage dealt is 1700*20 = 34000 damage, if enemies could survive that
Practice:
So, in real fight, imagine you are firing razorpine (3200 dps). Switching and casting magnet sphere requires 1 second approximately, so you lose 3200 dmg
Magnet sphere: 5635-3200 = 2435 dmg profit, stable since it auto-aims
Rainbow gun (cast it horizontally, to hit all foes), in frost moon gives about 1500 dps for 20 seconds, 30000 total dmg
Sure, its not stable, weaker enemies die, knockback-resistant ones escape, lets take 1/3 of the result, 10000 dmg
Rainbow gun: 10000-3200 = 6800 damage profit, unstable
Whats more, in pumpkin moon it is significally better (up to 3000 dps, 20 sec) against OOA its more effective against grounded foes than any sentry for 1 side.
Magnet sphere still does its 800 dps for 7 sec in any case.
I think with such a difference magnet sphere's stability is not that important
What are your ideas?