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.
If your Max HP is 2000 or less, a single shot from Lex will put you within execute range. With a headshot this goes up to 3000HP, and With Death Hastens these numbers become 2800 and 4200 respecticely.
Vivian’s only way to do damage to you is her gun. When the ultimate is up, she’s really dangerous.
Her sentinels have AoE, and their size is kinda big, too.
Try to focus her sentinels when her ultimate is up, so she isn’t so bursty.