Every so often, I like to go back and reread units to make sure I feel like I'm taking full advantage of everything my Codex has to offer, and sometimes I have a revelation. Most times though, I feel like I made a good call in never using something, like Fire Prisms (and the Night Spinner counterpart). And it's not just Fire Prisms either. I feel the same way about most tank choices that rely on a single gun with a large blast template to own face, and this includes vindicators and defilers for example, but at least they're already Strength 10 with a good AP. Fire Prisms though...just yuck. Sure, some people may tell you "dat's why you link 2 or 3 of 'em up and get a betterer gun to do da shootin' wit..." Congratulations on having a 500 point gun that automatically has a 50% miss built into it. Every time I watch a batrep on YouTube and see an Eldar lose and gt a confused look on their face because their Fire Prism didn't do anything, I just chuckle to myself.
There are so many things wrong with the Fire Prism, and for a proof of concept, compare it to a Falcon. The Falcon is the same point cost, has access to the same upgrades, and you can get 3 Strength 8 shots as opposed to the single Strength 9 shot (Strength 5 if you use the large blast). For a real kick in the teeth, the Fire Prism arbitrarily has BS4, but since it's a scatter weapon, you get the same hit chance as BS3...same as the Falcon! The last important note is that the Falcon is also troop transport. So not only can I blast you at long range with Strength 8 weapons, but I can hold an objective as well. Fantastic.
So what brings on this rant? Just so many "famous players" on YouTube who use this and seem to advocate it, but I've never really seen them do well with it consistently. In my opinion, check out War Walkers. These guys are my bread and butter, and every battle, tournament, league, etc, they've been by MVPs. My lists usually tend to include 2 3-model squads of walkers, each decked out with dual scatter lasers, and a Falcon with holo-fields that I keep a 5 man dire avenger squad in.
In closing, I'm not the only one on DED 'ARD who's gotten fed up with pie plate guns. A few of our marines players won't touch vindicators, and one who did own 3 of them, dumped them because of how little they performed for him. IG players have it a bit easier though since they can run their template producing vehicles in squadrons for better cost. I'd be very interested to hear if you have had similar experiences with your blast template vehicles, or if you even think I'm completely off the mark.