The lack of HP and resistances will make them useless in team fights where there is a lot of ambient damaged flying around. The numbers are also so low they will be killed at all points during lane phase. During PBE before they had ward HP, this was a huge problem.
Their damage is still pitiful, and I miss the old voidling. It will take 4 of those voidlings to make up for 1 of the old ones. 3 of these guys gets Malz a 120% AD ratio. (In total) and one of the old ones was 100% already. Then buffed at 7 seconds to 150%
They do get an akward scaling attack speed per level, but I don't really see that making a huge difference. They are gonna die, rather than an opponent choosing between killing Malz's damage or damaging him, most champs may kill the voidlings by proximity alone. Minions are going to have more HP than them, at all points of the game.
-Edit thoughts
I don't think a total of 20-60%AP ratio on a semi reliable basis will ever replace losing his old W and flat damage on his ult.
I used to be bummed out about losing AD Malz to this mess. But Malz going bot Lane because he can't go mid? This is truly sad.