If you are an effective quake player, then always quake.If you're not an effective quake player, practice. lol. She works for so many nodes, defenders, and matchups she can help a lot. (I wouldnt worry about dumping signature stones in her)The next suggestion would likely be aegon, he can handle a lot of act 5/6 content without much difficulty; unless you run suicide masteries, then i'd probably favor omega red.But really most of these champs are great champs and you really cant go wrong with any of them.
Domino. If you have the full flaming trinity (Masacre + Rulk + Domino) at decent star levels, obviously go for her. One of the best champs in the game, her heavy's incinerates DESTROYS opponents, it's so ridiculous. If you don't have the full flaming trinity, i would probably go for Aegon. I made a priority list for you, your welcome:1. Domino (Only with flaming trinity)2. Aegon3. Quake (If you have the skill)4. Void (If you need him for heal reversal or really long fights, or a utility machine, he's the champ to go for)5. Sparky (I still find him really good to this day and time, if you want a good hard-hitting, offensive champ. However, i wouldn't prioritise him utility-wise)6. Blade (Still very solid, but falls behind your other champs by a bit because he is unawakened. Plus, he kinda needs the holy trinity (Blade, Ghost Rider, Sparky) to compete with the others)Good luck!