Firepower:
Invested heavily in firepower. Again, largely ignoring Range Nodes as much as possible, because even with the emphasis on Velocity Nodes, beyond 500 meters is a crap shoot, a waste of ammo, and leaves you unable to effectively use your lasers.
Being a relatively hot mech, emphasis was placed on Heat Generation Nodes, while Cooldown Nodes don't help the heat issues, they do bring your LRMs on line much faster, for more effective barrages. Missile Spread and High Explosive were also important to maximize effectiveness of hits, particularly to internals.
Laser Duration minimizes exposure for snap shots, allowing me to twist and spread damage better (in fact it might be worthwhile to grab the 4th, I have to decide if it is worth trading another Node elsewhere, most likely from Auxiliary Nodes)
It should be noted I did try using a TAG but being so low mounted, I seldom found it a help, and in fact more often than not had lower damage results and early deaths because of trying so hard to get a TAG Lock. YMMV. I'd kill for a head mounted energy slot so that I could mount a proper TAG on my MDD.
Survival:
I messed with survival nodes, but even when I had 3/4 of the nodes unlocked, I only added 5-6 armor to each ST, which in my cost analysis simply did not seem to be a worthwhile investment. So I ended up skipping this Web for this build, entirely. There are other avenues to enhance Survival, notably in the Mobility and Operations Webs.
Mobility:
Not a heavy focus, but a small boost to my Acceleration and Deceleration, and tiny bit to my Turning. Still enough to make a noticeable difference in handling. Would not complain about more, but as a primarily LRM focused build, it does not "need" high mobility, and the MDD chassis is decent as an 84 kph 60 ton chassis to begin with.
Jump Jets: N/A
Operations:
The Most Important Node Web. This is a given on almost ANY Build. Without Heat Containment and Cool Run, you will be running into overheat on most "effective" builds. I missed one HEat Contain Node because I was unwilling to pay the Gate Toll. Still, by following my Node Layout you will get maximum results with minim "waste".
Hill Climb is of limited use, mostly on Assaults, and Speed Retention... YMMV, but I seldom find it helps survival much once you lose an ST or Leg on a Clan XL, and of course, on an IS XL, you are dead. Maybe once in a blue moon it could be the difference between getting to the dropship with a legged mech in Scouting, but again, cost analysis deemed that too rare a scenario to be worth the investment.
Improved Gyros are absolutely worth it, so following those Gatess on the way to opening as many Heat/Cool Nodes as possible is the best way. Minimize that screenshake from incoming missile and ballistics DPS builds.
Quick ignition, is of course just what it says. If you run a fairly hot build, you will inevitably shut down... starting up fast is pretty important.
Sensors:
The heart and soul of any good LRM build, IMO.
A relatively inexpensive investment of 10 Nodes nets you; 35% more Sensor Range (which stacks with the Active Probe), 400m Target Retention, 35% increase to Target Info Gather, and 3.5 seconds of Target Decay, helping to target and lock mechs sooner, Identify the weak spots sooner, and retain those locks much more effectively with all the active and passive counters out there.
Given the relative inefficiency of LRMs vs Direct Fire weapons, and the duration of exposure required to hold locks for yourself, etc, this is often the difference between life and death.
Auxiliary:
For this build, these are largely optional, but unlocking the first Node in this Web is really a No Brainer. For some, it might be more useful to invest the rest of these Skill Points in other Nodes, like Mobility.
For the way I run an LRM Mech being able to plant a UAV is more useful for me than an Arty or Air Strike, so I used that route to unlock what I truly wanted, which as you can guess, was enhancing my Cool Shot profile. Again, when I get in a position to use both Missiles and Lasers effectively, I can run hot, fast. This helps mitigate that to some degree, and can give me that added endurance when I must have it.
If a person is more inclined to set beck with their LRMs, then enhancing their Strike quantity and efficacy may be more useful than UAVs or Coolshots.
Mech Build and Node Summary:
So, here you see the overall build. In this case I paired ERMLs with the LRMs for more effective weapon crossover. More heat, but when fighting at that 350-450 or so sweet spot, it absolutely enhances your damage profile.
Active Probe is useful for enhancing my Sensor Range further (pairing well with my Sensor Nodes) and also for diffusing light ECM use.