yeah, bosses are bad examples. also, for the most part those blue spheres are avoidable (well, at least for my ninja skillz (tm)
i'd say dfp, because most classes tend to work off of that at a high lvl. some classes have really high evp, which can be worked into really nice blockalicious fun, but otherwise i have better things to use my armor slots for. and if anything, i'd use my material slots for HP material, because bloat is insanely useful for most classes. and somewhere around ult. ruins evp just starts taking too long to reach blockalicious fun.
about no-knockdown and block-lock, meh. i'm of the mind that this really shouldn't be a huge problem, either of them. after a while you should memorize where enemies spawn, and more importantly not let yourself get surrounded so easily. it happens, but for the most part it is highly avoidable. that's what schooling mobs and flinching is for, locks most mobs in a ball and ties 'em up while one keeps failing to attack. and with telepipes hotkeyed (mostly on 'droids) it should never happen (animation to drop and pop is too fast for enemies to surround). so i don't put much issue on that for this discussion. too often people forget to 'bravely run away' and reset the mobs.