It is not a radical departure from what came before and a logical progression from the 5S since the weapons and armor are almost exactly the same- 1 less DHS and switching to endo is where you get the weight to make the changes.
This may sound weird, but I think the -1 heat sink and the switch to ER medium lasers is what's messing me up. Playing previous Tbolts, I could stay at standoff for a while firing the Large laser and LRM 15, then switching to the medium lasers+a few small weapons if a foe gets in close range. Although one had to be careful with the 5S, this worked extremely well for me with the 7M and the 9S-they both seemed to have a lot of punch during a battle at all ranges, because it was easy to fire all 3 regular medium lasers along with other weapons.
With the 7S, that seems gone. The ER mediums eat up so much heat that any firing combos that worked in the past put me into heat penalties before I can do any damage. Or I try to mange heat carefully and just get out-shot and slaughtered. On average, I'm only hitting with maybe 1 to 2 weapons, for around 13 damage tops. Other mechs from the same time period (like the Wolverine 9M) can hit back for twice that amount of damage (Wolvie 9M with Heavy PPC plus Streak SRM 6) much more easily. And the extra 3 hexes of range for ER Mediums is offset by the fact I can usually only fire 1-2 tops if I want to fire other weapons.
That seems where I'm getting hosed...I can't keep up with the damage race. If I push the heat curve with the 7S, I get into movement and firing penalties much faster than other mechs or older Tbolts. If I try to keep cool, I'm not doing nearly enough damage to make any major impact on a game, even with support from lancemates. And the 7S just doesn't seem to improve durability enough to make it a good tradeoff. On paper, the 7S seems like it should do at least no worse than other Tbolts, but in every game I've played, it's performed significantly less efficiently. I had much better results swapping in an older 7M.
(Note: I have no objections to playing older or non-MUL listed Thuds in a Dark Age game, but I do like trying out mechs from the MUL, and the Tamar Pact and Hesperus Guards both seem to favor 7S and 11s. I wish they used the jumping 8M, which I REALLY like, or the C 2, which is a beast! Of course, I know I don't have to strictly follow the MUL for games, but I guess what I'm saying is I really WANT to like and use the 7S or 11S effectively, and I don't seem to be able to figure out a way to do so.)