The problem is, unless you can bring him down turn 1, and be able to make an insanely broken play next turn, there are other things you'd rather be doing with 4 mana (beats ala fatty, or establish lock pieces).
You don't want to cast this turn 1, off course you don't, 'cause like you said, you have soo much better things to do. I don't know why you think it's included for the option of playing it first turn. If your conclusion relied on the fact that you want to play it asap, you should overthink the card again.
If not, I would be interested on how you came to the conclusion that it isn't pulling it weight.
not only that, but the simulacrum does a job that you can do with other cards more efficiently in the later game. Although he has amazing synnergy with smokestack, it doesn't seem like his inclusion is warranted simply because he's a very good turn 1 play. In the midgame, wouldn't you rather draw something to win outright instead?
If you compare is to a fetchland, Solemn is better when you have a decent amount of mana, and are not in the need to play a first turn welder. Thus Solemn is almost always better.
Later in the game a Solemn is soo much better than a fetchland/mountain. It buys turns versus creatures and cycles at the same time. It provides a nice Welder Target, etc etc.
During the past few days, in which I did some extensive testing I have learned to appreciate the card. Right now I'm pretty certain it's the best card for the job.
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I have adjusted my decklist a little bit:
-1 Sundering Titan (too often I had to wait too long to be able to cast it, and than saw it just get countered)
+1 Mind's Eye (the single Eye proved good enough in non-control matchups to warrant a second one)
+1 Wheel of Fortune (I was worried the red manabase couldn't support this card, but I have rarely had problems with this)
(61 cards again

, help me out)
This also changes some minor thing in sideboard strategy, but not much.
Versus Tog/Hulk I decided too take out all Sphere of Resistances and Keep in the Chalices and bring in #3 and #4.
I also did quite a lot of testing versus Fish, and Masticore really shines in this matchups. And Chalice wins the game 90% in you resolve it with 2 counters. I feel the sideboard strategy and options versus Fish are very good right now and shouldn't be messed with anymore.
The next test phase is going to include decks that see less play, but can be pretty hard matchups. Mainly Dragon, but also Suicide (don't laugh, null rod + 9 LD can be pretty annoying)
Koen