The Jenner and Wolfhound are both perfectly capable of doing that in 3025 already
Very true. I should have written "Lights are much more often able to force PSRs on their own" in order for the argument to be understood better.
focusing fire is just playing smart.
Also true. But the key difference here is that the percentage of successful attacks from the 'Mechs combining fire gets lower as the tech level advances.
For example, take a lance of of -5S Thunderbolts, combining fire at a target 4 hexes away. For the sake of the example, all 'Mechs will want to remain heat neutral, so they'll be firing the Large Laser and two Medium Lasers for the highest potential damage at the best to-hit numbers. You have 12 chances to deal damage, and it would take 3-4 hits in order to force a PSR. So, at best, about 25% of the shots need to hit.
Now advance to 3050, and take a lance of -7M Thunderbolts. Because of double heat sinks, you have 28 chances to deal damage, and it would take 3-5 hits in order to force a PSR. So, at worst, about 17.9% of the shots need to hit. At best, 10.7%.
What this functionally means is that you end up seeing higher rates of damage, and therefore more PSRs on the table every turn. I *personally* think that the PSR part isn't super fun, because I find that Battletech is at its best when units are able to remain mobile (and w/ conscious pilots) for longer periods of the game.