So scions are a complicated army to play when trying to stay competitive. I'll point out the bonuses and negatives I've found playing with them and then ask you guys your opinions
Bonuses:
Plasma
Extra shots on 6s in rapid fire range
Reroll all wound rolls against vehicles and monsters
Can deepstrike into rapid fire range
Melta
When in melta range each six gives you another roll
Reroll all wounds against monsters and vehicles
Universal Bonuses
Yarrick - reroll 1s to hit so you can use your order on rerolling all wounds
Laurels of Command - Give plasma reroll 1s and reroll all wounds on a 4+ to avoid dying from overcharging
Negatives
If they have setup deepstrike blockers well then your plasma and melta won't have much to shoot at that's relevant
Good chance plasma won't be in rapid fire range for 2 shots and explosive 6s, melta can't deepstrike into melta range
Scions out in the open are just too easy to kill. 4+ with no invuln, 1 wound and t3. Even with go to ground they die quite quickly. And they can always just shoot another unit
Counter
Transports
Valks
are good because you can get out after movement, but have to disembark 9 inches away. If they've set up their army well even with movement after disembarkation you won't be with 6 inches with your melta and probably not within 12 with your plasma of what you want them to be in range of if you go first. If you end up going second and they shoot you valks out of the sky then you're left with foot slogging highly expensive troops
Taurox Prime
Fast, BS3 and good guns that explode on 6s at half range. Issue is their costs can be the same as a valk, only t6 and only have a capacity of 10. If you fit a 10 man squad of scions to max out on special weapons then there is not room for a Tempestor Prime to give orders. If you bring your TP down from deepstrike they may set up their force to prevent him from being able to give orders to a unit that's come out of a Taurox, and he also can't come down turn 1 outside of your deployment zone.
If you bring a second taurox you'd need to do something like bring 8 or 9 scions with max 2 special weapons to give him room to fit inside, or a command squad.
Biggest issue is getting the taurox to where you want them to go. Jumping out of them is great, getting essentially 9 inches plus base length towards what you want to get near to turn 2 but it doesn't guarantee your melta and plasma will be where you want them to be, and if you want to jump out turn 3 the taurox's are most likely dead by then.
Chimeras
If you bring a regular guard detachment you can bring chimeras instead, T7, transport capacity of 12 and cheaper. Can take double heavy flamer and be catachan for re rolling number of shots. Great for overwatch and taking out things like alaitoc flyers with -3 to hit them. Issue again is the points investment, not hard to kill, and even if you jump out of them your scions might not be in a good position anyway.
With all of that summarized the question I have is this. What Imperium army do you pair them up with to help lessen the effects of the issues I've spoken about.
ie. what would models/army would help with the following?
-Killing of deepstrike blockers
-Killing of chaf that stops models getting out of transports get to where they need to go
-Drawing fire away from the Chimeras (such as a Knight) to keep them alive going into turn 2 and 3
-Forces the opponent to come to you (hidden wyverns/manticores/mortar team) to bring enemy models closer to your threat range when coming out of transports, and means less turns going up the board to bring your scions where they need to go.
-Helps keep your scions alive once they've jumped out of their transports or deepstruck by killing infantry killing enemies or locking them up in
CC preventing them from shooting up your scions
-Use with fortifications?
-Anything else I may have missed.
Lastly, what's your composition of scions that you think would be most efficient? 20%, 50% 75% of your army?
Thanks for reading, I get that not many people use scions but I've got about 150 of them
Any feedback would be much appreciated, cheers