I agree that they shouldn't be freely available but I do think that there should be a melee weapon path available to tactical marines. The bolter and chainsword option is not that uncommon amongst tactical marines and power swords, axes, hammers and fists should be an option that is available to veterans, sergeants and captains etc. who have chosen to follow a melee orientated path. If you're going to be fighting nids close up in tunnels or enclosed spaces you're going to need tacs with an effective melee ability. Jet packs are about as much use as a chocolate teapot when there 's little room to manoeuvre and terminator suits are far rarer than tactical marines with a chainsword.