Welcome fellow Phaeron, as the others said (and they are most likely more experienced than me) you have a lot of gauss firing around and it surely doesn't help to have some different and/or more powerful than the standard flayer.
Personnaly I field a Doomsday Ark, it looks good and with str9 ap1 at 72" you have a one shot per turn beast. I also have some wraiths (1x whip coil) to divert infantry whilst the warriors smash them from the side.
Also in my experience I haven't had need to fully upgrade my Crypteks, at 1500pts I try to keep my list chap but larger...as a rule I take the Veil of Darkness for my Desptek and the
MSS + Phaze + Semp weave for Overlord.
Mate thought he'd charge my overlord without realising his 2+ save and 3+ invul LMAO oh how I laughed as his chaplin couldn't land a hit and died