Bulldozer will be your best friend. Anything that cripples as she get low on HP is almost necessary. CC reduction is also gonna be a big difference. Take out her foxes first enemies second, her healing is very solid so focus on her not the tank.
Buy "illuminate" from the item shop (at least to level 2 if your struggling against her), she will never think twice to go for you again as you will see her coming from a mile away!
Talus is a good champion to flank Dredge. Talus can disrupt Dredges flow of dealing damage and stop him from spamming his AoE (Area of Effect) attacks. Talus should kill him if he can but teleporting back to his portal is still ok as you dealt damage
Dredge may have good long range damage but he is very bad at dealing with flanks up close. It's best if he doesn't see you flanking him so a champion such as Skye is best.
Ruckus can activate a shield, if you are finding it hard to kill him then purchase "wrecker" from the item shop, getting it to tier 3 shreds through his shield.