Hi there & welcome to the hobby.
I'm afraid I skipped the SC box, so have never run the formation, but I think the general rule is that the starter formations become less useful above 500pts & that they are really just there to allow a new player to get straight into a game without needing to buy more units.
You lack a Character in your 2nd list, so won't get a Warlord Trait, also bear in mind the Lhamean can't join other units either, so she can't fill the final space in the Raider.
I would definitely add your Reavers back in also, I find they are one of our best units & can't be ignored by our opponents, which buys breathing space for the rest of your army.
As your looking to push up to 750, but I have no idea who or what you'll be facing, I'll just post a standard list as an example:
DE CAD 748
Lhamean, Cannon Venom (75)
5 x Warriors, Incl. Syb, Cannon Venom (115) - Warlord
5 x Warriors, Cannon Venom (105)
3 x Reavers, CC (63)
2 x Triple Lance Ravagers (250)
Talos, T/L HWB, II (140)
The Talos is to taste & there are many other things you could swap it for ie. another Ravager, Scourges, more Reavers. All depends who you face & how competitive their list is.
I run it as a distraction unit, straight up the middle usually, which draws fire from my Ravagers, which usually prevents Jinking, or if they ignore it, it usually kills something & they wish they hadn't. Obviously, sometimes it just dies, but that's the luck of the dice!