Those were the units I was listing when I was starting to list the only units that Lasher Tendrils would be useful against (well, I said 'Nettes rather than 'Stealers), but erased the list once it started getting long enough that the "only" bit wasn't very relevant--but if you fetch up against them often, by all means, go right ahead and keep that change in the list. As for suggestions... hard to fit in with just 1k points to play with, to get anything unequivocally better than what's already here, really.
I might swap one CSM squad and Rhino for 10 Cultists, just to free up aaalmost enough points for another 3-bike squad with 2 melta, or something (just camping the cultists out of sight behind cover on a home objective). It would be a tight fit and mean some tough choices to free up the last few points, but I like my lists starved and mean rather than glutted with all the option available, if possible, so I think the squeeze would be worth making.
What sphinx of plascrete and adamantium bashed open their skulls and ate up their brains and imagination? Imperator! Imperator!