There are IMO a few ways how arty work which are good, when using arty you have to know what you do and do it good otherwise you will be useless and die.
When you want to use long range MLRS you have to: get as many fobs as MLRS units and do not empty your teammates fobs. You need quite a few MLRS units to be effective, 4 - 6 is pretty effective.
Uhh, actually no. IMHO if you take 4-6 MLRS, you're missing the point and you're effectively giving the enemy the advantage on armor in numbers. You become a burden to your team and whenever there's no proper recon or the fighting is close up, you're completely useless. All you need is 1 FOB + 1-2 MLRS. It's a situational weapon. You do not spam it everywhere where you can see an enemy unit. Only fire corrected shots on specific targets. It's good for precision strikes on small/medium maps since you can fire a full volley so fast and the last rockets will be corrected in the right position - a real CV killer, and all you need is a few seconds of proper recon. It's also absolutely devastating when used in tandem with an armored assault. Fire a volley at the enemy concentration to stun/rout them while you sweep in with your own heavy armor. Their task is not to kill anything, just stun, panic and rout to make them easy pickings for your armor. I've been struck with this tactic a couple of times lately and there's pretty much nothing you can do when it hits you except run (well, hope to run before your units decide to stop and rout) or you get eaten alive. The third use of course is picking off soft units. Doom fortress forests and towns are prime targets.
Both tube and rocket arty have their uses but they're quite different and there's no "king" in that regard. Always remember not to overdo your arty, you still need base defenses and an offensive army to go along with your teammates.