Previous patch: LRM's were a nice long ranged, indirect fire damage tool. Not easy to avoid but there were some tactical manuevers you could perform such as using cover and buildings to block LRM flight paths or 'not get spotted/targeted in the first place' (my favourite with an LRM launcher, a Gauss and an ER Large Laser. Thermal view, x3.0 zoom, shoot what I can see, launch LRM's at what I could target.
This patch. LRM's are a primary weapon. Customised mechs with large numbers of LRM launchers and/or Artemis are lethal due to some arcing that seems to have LRM's being able to fly up and over buildings, slamming straight down the side of them. There are so many people packing these nigh unavoidable, next to skill-less menaces (previous patch LRM's required some skill to avoid wasting a large amount of ammo) that it's became a system of "If you're spotted, they'll launch LRM's at you and if you're not fast enough, you'll be nailed by most of the salvo." whereby when there are 2-3 people likely to be doing this to you at one time, surviving long enough to get some damage in on the enemy is a task which even 8x Atlas AS-7K's with 2 AMS each and unlimited would probably struggle with in this time.
Background: I was a Founder from early on and I've lived through various stages of LRM's. I've tested in every patch since Mid-July. In my opinion, the LRM's of the last patch were the most balanced LRM's we have had to date. Their lock-on times, damage dealt, avoidance capabilities, firing arc... all made for a weapon which could deal reasonable damage for a reasonable price and was something you could avoid taking damage from to a certain degree.
Now I'm not sure that Artemis IV FCS is to blame here. I think the LRM's may have been tweaked (intentionally or unintentionally) to give them such an arc that damage is hard to avoid. Couple this with Artemis IV FCS decreasing lock-on times and tightening the spread of LRM's then we have a weapon that does crazy damage. People try out this new Artemis IV, realise that it's powerful, use it more and more, more people start using it and the game becomes a bit of an LRM-fest.
My statements are not based on scientific fact but they mirror my feelings and my opinion, as well as possible causes, of this patch compared to previous iterations.