The challenge with vehicles in BATTLETECH is the balance of points vs. mechs. Generally speaking tanks cost less battle value vs. mechs as it equals out in that they can't make physical punching/kicking attacks and they are not as mobile due to speed and motive hits slowing them down- or immobilizing them. So as we move into heavy tank territory we need to balance out our tactica since now these tanks can cost as much as a battlemech. At 100 tons the Behemoth lives up to it's name: 2 X AC/10. 4 X LRM 5. 2 X SRM 6. 4 X SRM 2. 4 X MG. and LOTS of armor.
The Behemoth has the volume of dice to start hitting you at range with the AC and LRM packs- 6 "shots", so 3-4 on average are going to land. Unless you are fighting dedicated long range mechs, many mechs need to close to bring the medium lasers and other shorter range weapons that have good volume of dice. Do this agains the Behemoth, and it switches over to all the SRM packs plus the continued auto cannon fire.
Add the tanks armor into the mix and you can afford to trade shots back and forth for a few turns. At around ~1200 battle value the tank isn't cheap, but for what you get it is a value...
...as long as it doesn't get immobilized. Which unlike other hard hitting short range tanks like the Demolisher, at least you have ranged weapons and turrets to keep it in play. So the key tactica is to do our best not to get it immobilized and plan for it to get immobilized at the same time. The charm of Battletech is that sometimes a lucky hit happens- a head shot, double "1" chest hit, treads blown off and immobilized from the first long range shot.
You build in redundancy so you can keep going with some element of the unit and what makes it dangerous. I always take 2-3 as a minimum of any vehicle unit for this reason. I also try my best as I'm moving up the table to take a path that has fire options if I get immobilized- usually this is wanting to be in the center of the table as much as possible.
What heavy tanks scare you?