Okay, so Cavalier and I have been going back and forth about the new Blast weapon rules in 9th (which, to me, seem underwhelming). So as not to clutter up that thread any further, I'm going to elaborate on what I don't like about (specific) blast weapons and why.
In essence, the problem with most artillery in the game is that they are anti-tank weapons or possibly shooting small elite units, but are essentially worthless against hordes of infantry or even moderate numbers of infantry. This is only mitigated if you have a blast weapon that fires a minimum of 2d6 shots and does so at a modest price-tag.
To whit, the Basilisk:
While I readily concede to being out of the competitive game for a while now (my last tournament was in 6th Edition and then pretty much everyone around here stopped playing 40k except for a small handful), I can only see the Basilisk being useful if you have an opposing force of small elite units and vehicles (so, Primaris Marines or Bike lists or something) where a single shot has reasonable odds of doing significant damage to a fairly effective unit. And even then, there are a bunch of units the Guard can take that do that same job better.
If you play against anything else (hordes of Orks, hordes of Guardsmen, foot-tau, etc.), the Basilisk is, on a good day, going to kill 3 dudes on a shot for an extremely minimal return for a over-100 point tank. The range and all that is mostly irrelevant (when was the last time you were more than 48" from an enemy unit?) and so, barring niche uses where you've got an enemy hunkered out of LOS in the opposite corner of the board and no other way to get at it, it essentially is a big paper weight that nickel-and-dimes units all game without much to show for it.
So, okay, if your meta has you facing a bunch of small units that are small-arms resistant, then fine--fear the Basilisk. But hordes? Even moderately large units? Eh.
And that, right there, is my problem with blast weapons: they're pretty miserable horde control. You fire this giant cannon and routinely kill two guys. Now, if those two guys are pretty expensive (Wraithguard, etc.), that will hurt. But my ork opponent can let me kill two orks all day long and never care. Same goes for my own guard--shell away, I could give a crap. In an edition that gave us massive piles of dice for everybody else, blast weapons have been left behind. The Pie Plate was once king and is now jester. Or, I guess more accurately, a slightly better lascannon.
Maybe I'm alone in this (I guess?), but I really fail to see how 100+ points for an average of 4 (weaker) lascannon shots a turn equates to an effective use of points. Especially in an edition where (in my experience) vehicles have either become relatively rare or obnoxiously tough (Wave Serpents, Knights, etc.).
I would also add that, given the blast rules in 9th, big artillery guns really don't become much better against large units (6 shots hitting on 4s is still only 3 hits) and are exactly as good as they were against those small elite targets that have become their only real use.
I dunno, maybe I just don't play against enough marines? What am I missing?