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Thinking that this is quite an ultimate all-round shooting unit, whilst being a master of some targets in particular.

Give it a cheap HQ (say a librarian or Techmarine) with Memento-Mortispex and have Tigurius with the unit or Telion nearby as Warlord to grant rending. You will of course have to run an allied or multiple detachment as you will need 3 HQ to take Cawl to unlock the Memento-Mortispex, but he isn't exactly a tax - even if he isn't going to be re-rolling his FnP.
With Telion and a Techmarine with Memento-Mortispex you are talking as little as 310pts. You are then getting either 12 st8 ap4 Sunder (tankhunting) shots or 12 st5 ap5 barrage blasts. In combination to this the shots will have rending and either BS2 snapfire, Skyfire, or Monsterhunter. This means you can target flyers, Invisible units (even with the blasts if the invis unit is near another opponents unit as you can walk the blasts over), MCs, Mech, Infantry of all varieties (due to st5 rending blasts) etc. You can also very easily get a 3+ cover thanks to the techmarine.
With Tigurius you also get twin linked and a 1/2 chance at ignores cover.
Also roll with 3 rapier destroyers close by and if you aren't shooting invis/MCs or flyers, you aren't wasting the Techmarine with Memento-Mortispex as he can join to give these tank hunter which makes them insanely good at making explode rolls even against AV14 (39.5% chance from 3 shots).

I can't think of another unit that can take on so many different units so effectively at range. Is there a way to give IoM units shred that anyone is aware of?