So I am looking at the rules for one of the new super bugs trying to see what he is good for. He is a W6 Av2+ monstrous creature who with regenerate and choice of main weapon runs in at almost 300 points. Pretty hefty chuck of a 1500 point army. While they have some secondary armament that are like hull heavy bolters/flamers, these guys are all about their big guns. But this is really where they are lacking.
The basic choice is the Acid Spray which is essential the same in game terms to a hellhound's inferno cannon. The problem here is that the hellhound is a fast vehicle which means it can move 18 inches in a turn(twice the pace of a running tyrannofex) or move 12 and still fire the inferno cannon out to 12 more inches. So the tyrannofex is probably going to have a much harder time bringing this weapon to bear optimally than the hellhound. While you can use the Tervigon's Onslaught power to get it into range better this is another 160+ points invested and prevents that monstrous creature from shooting, running, or assaulting that turn. Sure the tyrannofex will be more survivable but you can probably get a squadron of 2 hellhounds for the cost of 1 tyrannofex. Here you are probably better off drop poding a unit of Pyrovores at lower cost.
Next Up is the Fleshboarer Hive with its 20 shots. This is the Leman Russ Punisher version except with S4 AP5 instead of S5 Ap -. The lower strength is fine if you are shooting at Av5+ troops but against Av4 or people with cover saves the punisher wins. The punisher also gets the advantage with twice the range meaning it can do its damage outside of meltagun, rapid fire plasma range, or non fleet assault range(powerfist in tac squad will keep this guy locked all game) . In the nid list, I think the newly out of favor dakkafex is better than this equipment since 12 Twinlinked Str 6 shots are probably similar in effectiveness.
Final Big gun choice is the Rupture Cannon. The name makes it sound like it will be deadly. S10 Assault 2 now that could put the hurt on something. Oh wait AP 4. So this is totally useless against MEQ infantry unlike any other S9-10 weapon in the game where if no good armor shows it self you can at least force a couple of marines to make coversaves if they have them. Since you are BS 3 your 2 shots get you 1 hit which has a good chance of penetrating most armor but then again you will be shooting at the front most likely so 13-14 is that standard armor you will be seeing that makes a worthwhile target. (Rhino's, Waveserpeants, and Chimera's are for Hive Guard putting out 6 times your shots on a per point basis). 1 Hit per turn, less than 50% penetration rate then 33% kill rate means you can expect to kill 1 tank a game with this guy. Maybe you will be lucky and get that landraider before it drops those thunderhammer terminators on you because they will own your monstrous butt in combat with 10 wounds to your less than 0.5.
Now you cannot compare this gun to the ordnance blast weapons of demolisher since they both anti-tank and anti-MEQ. The best comparison is with the Tau Railgun on a broadside. Both have solid stand off ranges, can be fired on the move(assuming upgrade to broadside suit never seen one without it), have 10 Strength, Twinlinked Heavy 1~Assault 2(not as good but close), but AP1 vs AP4 for that important +1 on the damage table. That +1 increase vehicle destroyed results by more than 50% (more vs those pesky holofield grav tanks). Plus while I do not know the cost of a Broadside I bet you can get at least 2 (canceling the shot advantage) plus some shield drones to increase survivability for 300 points. And you can hide in low level cover.
So the morale of the story appears to be that the nids big gun is really not big enough. Maybe you will find just the right situation for this guy once in a blue moon but most of the time you will probably wish you had something else like a 3 Hive Guard and 2 Zoans for about the same price for anti tank duty.