His list would be battle-forged if it had two more Guardian Defenders and two more Rangers; both units are below minimum sizes.
As it stands he's running almost 100 more points than you, too, and that just gets worse if you expand the Guardians and Rangers to legal minimum sizes. (I'm assuming no shinies in anyone's list, except a fusion blaster on one Stealth suit. Upgrades on the Serpent get expensive fast, but then, so do upgrades on the Piranha, Devilfish and Hammerhead)
So, for starters - have him run Eldrad as a regular Farseer instead. Not that Farseers aren't nasty, but bringing the points in parity will help.
What psychic powers is he using, anyway? You have to roll for them, so the Primaris powers are the only ones you can reliably count on a particular psyker getting. Eldrad gets four, sure, so he's got good odds.