Like hordes of horrors, even.
I like running "royal" valkyries, with the lascannon on it and the extra heavy bolters to augment the multirocketpods. All those things are going to cost you just as many points to buy on a squad of heavy weapons or in a 10 man gaurd unit -- but valkyries have bs3+ (hover) and can get reroll 1's. and can waft across the board to present easy firing lanes and then vanish offboard to keep from giving the enemy points from a crippled bird.

Seems like you have a 14 wound platform that is inherently -1 to be hit, with T7. Why not stick a lascannon and potentially 18 (really about 13) shots of s5/-1/1 on it? Its going to annoy, distract, and perform well.

Vendetta I arm up the same way. 3 of them are pricey, but 3 vendetta + 2 full payload manticores can often win the armor to armor fight while the enemy's dreadnaughts struggle to get in range, or their demolisher equipped leman russ tank commanders languish 39 inches away. I ain't saying that it is a perfect lineup, but you can cut big holes in a marine heavy infantry army with such firepower, while dancing well away from the massed bolterfire (that will have a hard time killing these birds in most cases). Remember you can slow movement with a kill from the flyers, too, if you have scion strats from PA)

Especially cause I usually have a tiny scions detachment at a minimum in the game, so the tempest prime is usually extra warlorded to bring old grudges. Now I can pick a single "easy to wound" thing ... one knight, one piece of enemy heavy armor, one critical monster, or one 10 man unit of heavy intercessers, and give all those shots of heavy bolter rerolls to wound (long as they are near the wld). I might point the lasers elsewhere, but the combination of OG and s5/-1/1 or 2 shooting from a few valkyries can cripple a big, expensive marine unit over a few rounds, especially if you are also stripping out cover with an astropath you brought along. 18 heavy bolters at 3+ with reroll 1's (in an army with just 3 valky) and another 6d6 s5/-1/1 (bs3+ with reroll 1's) is a pretty astonishingly good load of mixed dakka. To fight gravis armor use old grudges, then interlace 2d and 1d weapons so you can slowly chip away at the enemy without wasting lots of either damage type on odd numbered big marines. To kill just marines, doesn't matter the order so much, but you probably want to pick one unit to hit with just heavy bolters (kill, kill, kill) and one to hit with the other guns (wound, kill, wound, kill, wound, kill) so you don't waste any damage. Even a marine apothecary is going to struggle to keep multiple units up to full strength, if you are spreading the pressure around and killing a couple models here, a couple there.

Anyway, that's my thougth -- I think a valkyrie with full dakka loadout is better in your army for anti-horde than a wyvern is. Multilaser + 6 + 2d6 shots gives you about 16 shots at bs3+, wiht reroll 1's, and enough penetratoin to ignore ork armor, and enough strength to offset the wyvern's reroll wounds.
So a 24 shot wyvern hitting 12 times compares pretty well to a 16 shot valkyrie hitting about .. 12.5 times. You can however ALSO unload a squad or two of elite infantry (potentially adding in 12 grenade launchers from just the right spot that your opponent doesn't want to have to charge back to) for another 42 or so shots at long range. Or mabye you use it to deliever a bunch of scions up close with precision drop, and they shoot another 36 times. That's a trick you can't so easily do with the wyvern. Anyway, my point is, if you think of the valkyrie as a free wyvern that ALSO gets to act as a transport on turn 1 with a 45 inch range, remember a full dakka valkyrie costs only about 15 points more than a wyvern, which has 3 fewer wounds, 1 less toughness, isn't -1 to be hit, can't fly away, and can't cope well with enemy armor saves. A full dakka valkyrie with the lascannon on the nose may fire 2 shots less, but at 30 points more, it can mess up enemy armor in ways few wyvern can.