No. Tonnage is more a strategic decision. A light, fast, dodgey mech and pilot kind of works as a forward spotter for missile boats... but a single lucky shot usually ends their day.
But I don't use that style anymore. I load up on armor and direct-fire alpha damage and heat sinks and focus on morale options on ship upgrades so that the first encounter with the enemy results in at least 1 dead enemy mech. I don't have any dead pilots yet (knock on wood) because I make use of that second morale skill a lot that allows me to break coverage, dump stability damage, and lose LOS when I see trouble brewing.
My style prioritizes 2 to 3 high damage weapons of medium to Long range per mech and enough heat sinks to allow a full strike with no more than 50 net heat. If you alpha damage a mech's CT and destroy it you usually get a morale boost tat allows you to do it all over again.
I only use missiles that are +Stb or +Dam since knockdowns become so important, and a missile damage bonus is per missile, making for HUGE damage boosts with LRM10, LRM15 and LRM20 weapons. I tend to collect them and then build a mech that is nothing but ++ or better missile racks. They make a great "OH ****!" button in a lot of missions.
Edit: OH, also, all of my pilots take targeting, and my missile pilots take tactics. I have one dedicated brawler (guts2/pilot1), but she spends most of the time in the hospital.
Here are my favorite mechwarrior builds:
Guts2/Pilot1 is super fun if you can get in to a fist fight.
Target2/Pilot1 Run and gun is the master class. Standing your ground for a round and just shooting will get you killed. Try to always move as much as possible every round to build evasion chits.
Tactics2/Pilot1 Great for a situational missile-boat pilot as they get really good target bonuses on indirect fire.
As you can see, I find Pilot1 to be almost essential