The thing is, both the Rifleman and the Jagermech are both viable designs, for the battlefield, in the same way that the Sherman and Hellcat were viable. To use a WWII analogy, and only as a comparison, not an argument, they are similar to the Sherman and the Hellcat tanks. Neither really had the armor to stand up to the opposition that they were facing, but, by the time that the weaknesses were known, the Allied forces were in a position where taking the time to retool the production lines would have created a shortage of tanks, and could have cost the allies the war. At the same time, it was the weaknesses of those designs that were creating the losses that required constant production to replace. And with the need to ship across the Atlantic, there was no way that the design could be altered, or replaced.
The Inner Sphere faces the same issue --- most mechs are being shipped to very far away locations, and with the limited shipping capabilities in the Inner Sphere, not enough are being shipped to create the surpluses needed to give time for a retooling of the lines. So, the factories keep churning out designs to replace losses created by the weakness of the design that is being created.
The second complaint about the Rifleman, and other designs mentioned, seems to be the autocannons, which really goes more to show the metagame aspect of tabletop play, versus the attitudes that would be found in the universe. For one thing, you have to look at the armor, before you can judge the autocannons in game. One thing about Battletech that people need to realize is that Battletech Armor is radically different than any other armor. In the real world, we do not use the 37MM guns from the M3 Lee, or the Panzers II and III, because they no longer have the ability to damage the armor of modern vehicles. However, in Battletech the AC/5 does 5 damage --- it does 5 damage in the Star League, it does 5 damage through all 300 years of the succession wars, and it does 5 damage all the way up to 3145. That's a 500 year span, right there, and the AC/5 was developed prior to the Star League. Plus, pretty much any planet with metal deposits and a machine shop can make one. Add in the fact that AC's seem to be very flexible in ammo types, as in AC/5 ammo for the Wolverine will fit the AC/5 in the Marauder, the Zeus, or the Rifleman......and you have a good reason for it to have survived. Along with it's ability to be used as a field gun, by infantry.
Now, I know that people have stated that lasers are easy to maintain --- just polish the lenses..... true, but what if they crack? What if one of the capacitors gets damaged? What if the software that tracks the laser energy output and feedback gets corrupted, or a power line cut, due to battle damage, etc. Some of these things, such as damaged electrical connectors can effect AC's too --- but the parts for an AC are NOT as technologically advanced, as are the parts for a laser. You need more precise manufacturing to make a lens for a laser, than you do for an AC.
On the table, from a purely stats viewpoint, AC's make no sense.... and to a NON-Military mind, should have been phased out. From a military standpoint, it's a lot like the issue the US Army had with Helmets --- we developed the PASGT Helmet, which is the one that we just replaced, during the Vietnam War, but it was rejected by the Army, due to it's resemblance to the German WWII helmets. It wasn't accepted until the 80's ---- so it took a decade for our army to accept a superior helmet, based on it's look.
That would be how mech pilots would see the AC --- it worked for the first mech --- it worked for the Star League --- it worked for the Succession Wars --- and it works against Reflective Armor, or Reactive Armor, now.
The first armor to ever be specifically effective against AC's doesn't show up until FM3145 with the Ballistic Reinforced armor --- and let's face it, getting only 12 points per ton, means that you are paying tonnage in armor to half an AC.... while beam weapons do normal damage. I really don't see a LOT of mechs going for this option.... meaning that on a modern battlefield, the old reliable AC is probably still just as effective as it has always been. Especially since Reflective Armor still gets 16 points per ton, and can be very effective against energy boats.
So, yeah, the AC is not as effective, and by definition, those mechs, such as the Rifleman, are not as efficient, but that is a metagame bean counter view of the universe. Within the universe, people are more likely to see if differently... as it's not likely that the average person knows the exact damage that a weapon does..... we use fixed damages, but in the universe, there would be glancing blows, or ricochets, meaning that the damage would be less consistent, which means that AC's would remain viable, as would the mechs that use them.
The Rifleman is a solid design.... it has flaws, and like so many other designs, things could be done better, but it does work.
Nahuris