The only place where picking even one AMS whenever you can is a bottom of Tier 5 (still very arguable). From my personal experience across the tiers, I developed some rules as to when pick AMS (only one, never more) and on what mech:
1. If I have spare tonnage with slots and really NOTHING else to spend it on.
2. If I run Assault or very immobile Heavy to help myself mitigate some missile damage before I can get in cover, plus I have spare tonnage and slots for it, never a priority.
3. Avoid L-AMS if I have at least something that produces heat.
I never pick it for "help the team" reason, because it won't help anyone who can't utilize cover and caught out of position, and it will help people who can even less. AMS can mostly protect from LRM fire, much less from any other missiles, since Streaks, SRMs or MRM are usually too close to mitigate good portion of damage, and ATMs you can just dodge, twist or shield even in very slow Assault. While L-AMS is hilarious, especially triple one. Seeing some guys frying themselves and exploding while not even getting shot at is priceless.
On the other hand we have ECM. I still don't prioritize it over additional firepower, but it holds FAR MORE utility than any number of AMS ever could IMO. With maxed nodes, you get decent bubble, which can protect you well and your team from locks, delay detection, let you re-position or move less noticeably and break locks faster when you or your teammates breaks LOS with an enemy. Not to mention that two mechs with ECM jumping anyone with lock type missiles and BAP, completely jam him, and not only missiles but impair ability to get target info at all. With so many advantages (among stealth armor, which can be quite gimmicky) you still don't have to (and can't) "boat" ECM, no heat, no need for ammo, no downsides at all.
So when I see threads like: "Uh, look! Triple AMS Nova! All Lurmers run for your lives!" seems a bit strange, since there are several heavy boats, they can still break through triple AMS, if dude is standing in the open or somebody behind keeps locks at it, but with ECM, it's much easier to avoid sustain fire.
Edited by Dragonporn, 27 May 2018 - 05:36 AM.