Mediums have no purpose currently due to absence of tonnage restrictions per drop.
However, saying that mediums are worthless is r*tarded. Sure, you won't win a 1v1 close range fight against an assault or even a semi decent heavy, but mediums can carry a surprising amount of firepower, though they do require an XL engine to do so. Long range is trickier, since there are some mediums that are exceptionally good at it. The triple PPC 4P Hunchback is a prime example of this, followed by somewhat inferior gauss+ERPPC Blackjack or the double ERPPC blackjack jumper. These mediums are fast, have small profiles and have all of their weapons located in a single high mounted location. This means that all of their projectiles emanate basically from one point (this is where we remember why the 3PPC+gauss highlander is so dangerous - due to the fact that its 3PPCs and gauss are located very close together, reducing convergence problems to minimum and guaranteeing that all of the projectiles will hit the same location EVEN on a moving target that is being led). The high mounted weapons also give you the ability to "ridgehump" extremely well and the double ERPPC jumper blackjack can even poptart (which it's pretty good right now, because it has very small reticule shake, compared to the Highalnder or the Cataphract 3D). Of course, none of this guarantees that you're going to win in 1v1 shotoout against a PPC stalker, but you can be a major pain in the *** even with inferior firepower and armor.
If tonnage restrictions were in place, I think that mediums would have a very interesting role to fill: the role of fragile, but quite hard hitting long or close range mechs that are significantly lighter than heavies or assaults. Using mediums would allow drop commanders to significantly complement their team's firepower while saving overal team weight and possibly picking an extra assault instead of a heavy or just heavier assaults. We have been running long range mediums for quite some time now and matches where a triple PPC Hunchback is the mech with the highest damage output out of both teams team are quite frequent.
TL;DR: mediums are inferior to heavies and assaults and there's no real reason to pick them right now due to lack of tonnage restrictions, however, they will become very useful IF PGI gets its sh*t together and adds tonnage restrictions to at least 8man matches.
Something else I wanted to add: a "meta compliant" medium is better than a "non meta compliant" heavy in many cases. Seeing how many pub matches involve poorly configured heavies and mediums on both sides, one should not feel like he's gimping his team by bringing a properly outiftted medium to the team. Of course, this reasoning flies out of the windown when you're facing teams of 8 assaults, but such matches aren't as frequent as some people would want you to believe.
Edited by Leimrey, 04 July 2013 - 02:51 AM.