After noobing with SM im trying IG for a while. I noticed that against tyranids and orks its almost impossible, mostly against melee spam. I usually go with sentinel + guardsmen + 2 sergeants + catatchans at tier 1 but catatchans arent enough. I managed to coordinate a grenade barrage, then an explosive shot and then a stomp on a 4 sluggas that came for me but the remaining ones (half of them) were enough to obliterate my forces. Also if I retretat the motherfukkers with their melee charge always catch my forces and just kill them... Im mad at this because I have to basically engage and retreat and they still can damage a lot. Catatchans or ogryns or assault marine squad or melee leaders dont have melee charge...
So basically how the hell should I do this? They obliterate me at tier 1. Even if i go to tier 2 a manticore isnt useful since they arent idiots (however it works wonders if you play against a player that doesnt pay attention). Ogryns are but they get obliterated against 4 upgrade sluggas + 1 truck and they cost a ton of requisition and power... Which If i manage to amass the battle is almost over.
Also I have the doubt about what to do if I lose a basic squad like a tactical marine squad or a catatchan squad at tier 2/3. Should I buy another one or just move on?