It's not so much that the 3D Marauder is close range as it not being totally a long range machine. At shorter distances, your to-hit numbers improve, based on your armament. Unless your guns have a minimum range. For the PPCs, 4-6 hexes is best. 3 hexes gets you a plus 1 (Plus is bad. Both Battletech and Mechwarrior are roll under systems.). 2 hexes or 7-12 both get you a plus 2. Being adjacent nets a plus 3, and from 13-18 a plus 4. So, even at point blank range, PPCs are still better than at long. This is usually the case with most weapons save LRMs. (At point blank range, they get a plus 6. When anything over 12 can't hit at all, and it's usually added to a 4 to start off with without taking into account either machines' movement....)
Plus you have the other weapons. A large laser and a pair of mediums are quite respectable. A large laser is actually a longish ranged weapons, but firing it in concert with your particle guns will rapidly shoot your heat through the stratosphere and quickly degrade performance.
So, the 3D's arnament are good at most ranges. So closing is okay. Hanging back, though is also okay. In many cases, it is even preferable. Many mechs use short ranged weapons as their main guns.(The standard Hunchback for instance has no weapon with a range greater than 9.) It's good to have better to hit numbers, but it's even better to be where they can't hit you at all, especially in the case where they're trying to hit you with a 20 class Autocannon (The absolute most vicious gun in the game.), as in the Hunchback; or a quartet of medium lasers, an SRM 6, and a pair of machine guns, as in the BattleMaster. Though a Battlemaster packs a single PPC for long range, the 10 damage is better than the 36 it can potentially nail you with in close distances. And having that split among 6 guns means he has a chance to hit you with at least something, as proposed to a single sniper weapon that is all or nothing.
So it's often based on your opposition.
Another determinant for what range to engage the enemy is physical attacks. Usually, heavy is better, as damage is based mainly on weight. The Marauder's kick at 15 damage, is devastating. However, it has thinly armored legs. So if a comparably sized mech kicks back, it can quickly become overwhelmed. Even worse for punch damage. Usually, a 75 tonner will get two 8 point 1 in 6 chances of hitting the head of your opponent. But the Marauder has no hands. This halves the damage, to a fairly crummy four.
So, at close range, the chances of physical confrontation increases, which is, for the Marauder, a very mixed bag. In BattleTech, almost nothing is cut and dried.
So, just some things to think about.
