Well, the list has a good idea, but some things are messed up, no offense
First of all, i've found that the only good mix between leman russ is Demolisher+eradicator or Punisher+exterminator... then, the manticore is really a fun model to field, but not so strong, sadly..not now that you can field so many high strenght stuff...also, the mix of special weapons in veteran squads ir rarely a good compromise, imo
I'd go with:
Pask in Punisher + HB Sponsons
Punisher + HB Sponsons
10 Vets, 2 Melta, with Commissar, in Taurox
10 Vets, 2 Melta,, with Commissar, in Taurox
Demolisher tank +H. flamer hull
Eradicator tank + lascannon hull
This way Taurox and meltavets can support the advancing demolisher/eradicator squadron, to kill vehicles and hordes alike
Punishers work with the knight against any threat (lots of dakka + a melta blast & D attacks is nothing to sneeze at) while Manticore is there as an unpredictable punch in the groin. It may as well be wasted points, but if it decides to work properly...BOOOM!
Basically your list, with some different organization, points around 1450 ish...
What do you think?