I think with some fine tweaking Our power level on killing things actually got alittle better with the Basic DE Book, To me it seems that the DE book is Fire power and the Cover book have Staying Power.
Both books have alittle of the other in them, but each book focus for on one than the other.
5 Talos: thats 15w at T7 with 3+/FnP with Scout, if you Add a Cronos behind them, they will have 4+FnP, Put some HWB's on them, now you have a Living Walking AT/AI super unit. Tho this will cost 800pts. But, it unless they have titans/D-weapons blasts, not much will kill them in a couple turns, I If my math is correct, it will take an average of 8 Wave Serpent's full firing to kill that unit.
The DE book seem to be trying to do Alpha strike with Guns and then mop up with Melee turn 3-4 with our Rampage units/bikes.