Ooh, very good points all around! I hadn't thought of some of these things. Really good arguments!
I'm not quite sold on Force Hammer. There are some books that I include one or even two, but mostly in Forcemaster-books. For the same amount of spellbookpoints (or even less) I can include a Hurl Boulder, which has the same Slam-chance, but one die more against creatures. It has one fewer die against conjurations, but I believe that a Force Hammer always comes short against conjurations that really matter. 8 dice of damage versus a Wizard's Tower? That's 7 health and 3 armor. Probably won't kill it. I just wasted 9 mana and 7 dice on the enemy mage. Battleforge? 6 crits on 8 dice? May work. But it could not work as well. When it's really important to bring a Battleforge down, I'd rather use 2 Geysers for 8 mana and 12 dice. They'll probably give me my 6 crits.
You make a really good point about Hurl Boulder. Eight mana and it rolls seven against creatures and conjurations alike. It is slightly more versatile, and I see what you mean about not being able to kill conjurations. It's a bit risky to count on Force Hammer to roll well enough to one-shot conjurations.
I agree that some conjurations can be a nuisance, and while others have suggested casting two attack spells and other options, often the conjuration you need to take out isn't susceptible to that damage type (e.g. while 2 Geysers work great against Battleforge or a Wall of Fire, they won't help you against pretty much anything else) or you can't afford the actions to cast two attack spells.
I also agree with this. I feel very torn about surging wave, for example, as an answer to battle forge. In general a lot of attack spells that are there to deal with specific conjurations just feel like dead weight once the conjuration is dead or if for some reason you have to fight through some creatures or walls to get to the conjuration. That's one of the things I love about Mage Wars, there really is no cut and dry solution for a problem. There are many effective spells, but often there is no "hard counter."
This definitely changes my thinking about Force Hammer and I can definitely see why some people don't run one in every deck.