Depends if its dual wield or not and content type, pve or pvp. With DW, even if enchantment potency is halved, 2 status effects at the price of one will be better than double dot poison. With non-dw its debatable, total damage of double dot poison could be marginally be better than single enchantment.

As for PVP there are a couple factors you need to take into account, like if you want to buff your damage or debuff the enemy. If you want to buff your damage, shock glyph and absorb stamina can provide minor vulnerability (through concussed) and minor breach (through sundered) unless you already have those in your skills. For debuffing the enemy and overall making their life miserable, immobilize and increase cost poisons are generally better options.