hey tom -- i'm glad you asked about morph, i've been wanting to write this one for awhile. i love morph. morph is just fucking great. it's my second-favorite draft mechanic of all time (after cycling obv). however! finding fun morphs within the context of my cube is difficult to impossible. here are the ones i've considered:
bane of the living
blistering firecat
brine elemental
chromeshell crab
exalted angel
fathom seer
fortune thief
hystrodon
nantuko vigilante
soul collector
thelonite hermit
vesuvan shapeshifter
one of the problems with morph is that it costs a lot of mana. in ols/tsp draft this enables you to sink so it's a perfect mechanic there, in cube though there ought to be better things to do than turning a bro face up. the main offenders here are bane, brine, crab, hystrodon, vigilante, hermit, which leaves:
blistering firecat
exalted angel
fathom seer
fortune thief
soul collector
vesuvan shapeshifter
cat is terrible, the aggro decks aren't burn decks. seer is not powerful enough, there are more flexible draw effects out there. vesuvan shapeshifter is very cool but i'm already stocked up on clones (p. image, metamorph, spitting image, sakashima's student) and five mana is a lot. this leaves:
exalted angel
fortune thief
soul collector
i like these cards a lot. the issue is that morph is (subtly) a parasitic mechanic. like splice or soulshift, it requires a critical mass of cards to work well -- with only three morphs in the cube, the element of surprise and wonder is more or less absent. i could add more cards, but supporting a morph theme isn't worth it. part of good cube design is not supporting themes that need too much support to work with the gestalt.
so that's why i don't have any morphs.
other cards: we haven't drafted with helm yet, i'm excited for it though. effects like that get a bad rap because vedalken shackles is a fucking disaster but when fixed to a reasonable power level they are fun. for example, i've been happy with callous oppressor. (for my conventional control magic effect, i favor sower -- powerful but easy to interact with, easy to get blown out with.) i'm not sure anyone ever drafted harm's way (i also tried faith's shield in that slot). there's a lesson about how all sample sizes are insufficient and cube testing, like brewing, is going to come down to the subjective judgments of you and your playgroup, but i'll go into that somewhere else.