Well, it is up to the player how far can go and is interested in the game. The way I progressed was through consistent farming in order to be able to myth parts as actually still doing. Back then because the amount of farming I used to do; I was making my own legends from Epics. Because the fast number of parts I wanted to work on simultaneously, I even used to make common to rare and rare to epic to keep all moving as I wanted.
That was my way because I was rushing for my own fun.
It is worthy to make Legends from EPIC [arts to use as meat? Absolutely yes and that including pay to win players. If someone say no, well... it is not a grinder or player that likes to make parts and lazy.
Those are some pictures from my own progress thread comments. Those check marked were parts ready to transform to legend for myth transformations.
What do you have to understand is that eating EPIC parts, you need to be 100% that won be a part that you might need in the future regardless current set ups. EPICS parts sometimes repeat but sometimes in the freeway don't and can suffer if not do things carefully if building a serious account.
In the pictures above, some of those parts are real need for any account but for my account were not in need having enough for 3 mech set for those parts. Some others were real meat.
For example. you can use these parts to transform and then eat.
You will not suffer anything using them.
Now, parts like these below as example, can be a risk because are real weapons for future use and for some ranks to advance.
Use criteria checking parts stats.
Meat
Meat
So, pick a part at EPIC that can pass to legend but no divine status as base of considerations. Remember that parts arounds some reach some status higher than others but not all are provided in EPIC. You might need to make even Epics to supply the transformation to legend.