This [Sly Vulpaphyla] build's purpose is to keep balance between gaining sustain on your warframe and buffing your gun's DPS output.

Gaining DPS is pretty simple and basic: [Reinforced Bond] and [Tenacious Bond] are so strong right now, and they need

Calculated Redirection and Hunter Synergy to work well (IMPORTANT: If your primary weapon doesn't have 100% critical chance or more, either swap Hunter Synergy with Bite or just drop Tenacious Bond and Hunter Synergy for other mods affecting recovery time or increasing vulpaphyla's defenses.

Rest of the mods increase our sustain:
Synth Deconstruct increases health orb drop chance from killed enemies - that works great with Equalibrium on our warframe. It's great way to refill energy.
Martyr Symbiosis Protects us from lethal gamage and we are invulnerable for some time, however vulpaphyla is dying by saving us and cannot do that until she recovers (30s). We want to be protected from lethal damage all the time, so shortening recovery time is the main point. I'm using Restorative Bond and Tenacious Bond, but you can use sth else, for example [Medi-Pet Kit] instead of Tenacious Bond would work somehow too.
Tek Assult gives a chance that vulpaphyla just won't die when it should die. That's a good deal in case we don't wanna die because if vulpaphyle doesn't die - so do we.
Signature mods (Survival Instinct and Sly Devolution) in addition to mods above make us pretty hard to kill, because while we're killing enemies, we're harder to hit (enemies are less accurate), so we're taking less damage and there's more time to click panic button when our shields break, for example '5' and Protective Sling with Vazarin focus school, Rolling Guard or whatever helps you stay alive. Ofcourse if our pet is up, you can take lethal damage and still stay alive, but if it's downed and you have no way to survive next few seconds, you're pretty much f**ked.

This is the build that works for me the best. Hope you enjoyed a guide. Take care :)