The answer, as usual, is: "it depends".
After Asymm2 the stude should be convinced that it will take him/her 100-200ft to sort out an engine failure and get the beast climbing again - and this was when they were expecting a failure because it was the asymm part of a ME course! Ask them how they think they would cope in 11 months and 25 days on a hot day at MLW! I was taught to teach a Vach of 300 ft and this seems to work well for the average stude in a Seneca 1 (with an addition of 100ft or so if an asymm approach is unavoidable in IMC) but in a Duchess (e.g.) 300ft would probably be excessive (but safe). As always: know your horse and stay in practice.
On a slightly different tack...
I recently had a candidate for his first MEPL renewal who (he said) had not been given the full asymm long brief during his training or shown the advantage of 5 deg bank towards the live - I won't mention the airfield for fear of libel suits
Please peeps, give your studes the long asymm brief and teach them about the bank attitude for zero side-slip.
And on an even different tack...
I tend to end an MEPL course by failing an engine below Vach - it's surprising how many people try to go-around despite having said LAND, lowered full flap and started slowing down as they go through 300ft. It leads to some interesting aircraft attitudes before self preservation leads to an "I have control".
RAGA before Vach, commit after Vach.
HFD