Alright so I'm going to give you a step by step as to yes or no, and why.
Overlord, they're amazing, but a 3+/4+
rp is only so good with all the strength D running around, take the solar staff off him and give him a phase shifter and a war scythe. Troops look fine, I would suggest disembarking the warriors so that your arks can contest tactical objectives, unless your plan is to bubble wrap them(Beware of flamers). Tomb Blades, I would take the +3 armor, on half and the +3 jink on the other half, and put whichever is strongest out in front but band them into the same unit, yes this means one less unit to grab, but units of 3 die easily, units of 6 not so much, also, as awesome as our gauss is, I'd make room for some ignores cover blasts, great for taking out pathfinders in cover and amazing against tau in general. Drop that cat barge, because he'll get popped the way he is kitted, with all the high strength stuff being thrown around in these high points games, take nemesor zandrakh stick him in a blob of warriors, for his adaptive tactics(this will also help for bringing in the night scythe on turn 2). It also gives a unit of warriors fearless, so less chance of a sweeping advance, you can also drop Obryon without scatter if hes next to Zandrakh. I'd also try and take an extra cryptek with a solar staff, to give that extra cushion with your lychguard unit. This way you could ghost walk them across the board, pop the solar staff, and only worry about snap shots and melee which that unit is good for. No issues with the deathmarks except I'd try and bring a 10 man squad.
This will be a little easier, again, no cat barges, they used to be ok, but now their good in like 1000 point games or lower, especially if you don't plan on kitting them with an invuln, they're gunna be an easy first blood/ slay the warlord. For a smaller list like this though I'd bring Szeras, and more warriors, using his bubble to up the
RP of all units around him, gives you a good central hub for your monolith. Truth be told you'd be better off bringing a cad, giving all your ghost arks and troops Objective secured, which will win you tactics games. You can also use a ghost ark in a cad to help fling your lychguard. Since you can only put warriors or characters inside the ghost ark, you can put the royal court inside, and fling them up the center of the field, to join the unit of lychguard that just deep struck in your opponents face.
Your idea of having multiple small man units isn't bad except that they'll die off easier in shooting, and less of a blob dies faster, you want to utilize your ghost arks repair feature, to help bring back fallen warriors, and just tie tie tie up people.
Other then that the only issues I have with your lists, is that you're not running a harvest, which is awesome, because the scarabs can take down most imperial knights by scarab farming, and the wraiths tar pit and kill almost anything. They become more tarpitty, as part of a decurion as they become a 3+/3++ with a 4+reanimate, also they gain relentless as part of the formation, which allows them to take their exile rays, and assault in the same turn. You wanna see your opponents face drop, watch when you roll 6 shots for overwatch, score two hits, and then exile a dreadnaught before it gets to do anything(has been done by me at least twice.)
I'm always more then happy to bounce ideas back and forth about lists and why, and as
op as the decurion is I don't bring it because I find it takes away from both players fun. You wanna get into some real fun, bring CADs, with formation detatchments of Harvests, and conclaves of the burning one.
Any questions feel free to shoot me a
PM as i might not see this,
Nemesor Blackwing
~6000
~2000