I'd agree that a lascannon is probably not the greatest weapon choice for a tactical squad. Missile launchers or heavy bolters tend to be better picks since they're more cost-effective and, in the missile launcher's case, more versatile. If you're not mounting up in Rhinos, then I'd distribute plasma rifles to each squad-- the better range offsets the risk the weapons pose to the Space Marine carrying them, in my experience, and 24'' is nothing to sniff at. You might also consider a plasma cannon somewhere. I've found the most effective semi-static Tactical Squads are those which are equipped to fight Space Marines or the like, as they tend to have high-strength heavy and special weapons with low AP, but still retain some threatening close combat ability. A veteran sergeant with a power fist is probably a must.
Admittedly, I tend to field my Tactical Squads in Rhinos for the added mobility (and ultimately cover that the destroyed vehicle provides), and I use the Trust Your Battle Brothers trait, but my Tactical Squads are generally equipped as such-- even without True Grit, it's quite effective:
Lions Rampant Tactical Squad Assault Configuration
-Sergeant armed with a power fist and boltgun
-Eight Astartes armed with boltguns and close combat weapons
-One Astartes armed with a meltagun
-The entire squad has frag grenades, True Grit, and Counterattack
-Rhino APC with extra armour, smoke launchers
When I get the urge to hang back a bit more, I tend to still give the squad True Grit/Counterattack and frag grenades, purely because you never know what's going to happen and since you have so few models on the table, it's good to be prepared. Instead of the melta, I'll usually issue a plasma rifle and either heavy bolter or missile launcher. Either way, the squad is still highly flexible, which is ultimately what you need from Tactical Squads.