I also tend to agree that the Assassin is pretty under apprecated and under rated. Yes, its mainly under rated because its rated a 1 when its really a 4, and even the best mechs in that role are 2s or 3s in that era, but still.
As has been aptly pointed out, if you want a 7/11/7 mech in that era, the Assassin and Spider are the key choices, and while the Spider has its advantages (its a bit faster, and with two lasers it hits harder in close and has no ammo woes) the Assassin is a perficly competitive choice, adding in the ability to hit at range, and with better crit seeking and better heat managment vs the Spider, along with the better armor. So, if you need a mech that is fast that you just want to have to cause trouble, then the Assassin is a great choice. Because it can position itself very effectively, and because with its +1 TMM realitive to mechs that only jump 6 or run 9, it can get closer to enemy mechs more safely, and employ its minimal weapons quite well. Relitive to a lot of comperable 6/9/6 mechs that seem to be more powerful, the Assassin is likely to do nearly as much damage, and to the right mechs at the right time in battle. People look at the PHawk or Vulcan with the MLs or Fire Javelin or Jenner and it looks like its pretty lacking, but that extra MP or jet makes all the difrence sometimes, because you can be where you want to be, when you want to be there.
Would it be vastly better with a number of key modifications? Yes, there's little question about that. But, is it very usable? Yes.
And, of course, if the Jenner had 7 jets, no one would ever use it...