Naw, it's normal to see +1 in heroic.
I think difficulty goes something like this (i can be totally wrong tho).
Heroic - 0/+1 normal sized groups.
Tenacious - 0/+1 larger sized groups.
Rugged - +1/+2 normal sized groups.
Unyielding - +1/+2 larger sized groups.
Invincible - +2/+3 normal sized groups.
There are of course exceptions, some missions will have various level spans (Atta mission in Hollows is a good example, goes from like -3 to +1 on heroic), some will for example only spawn LTs or only Bosses etc.
Must just be me then but I don't ever remember having so much trouble with any AT before. Oh well, I'll persevere...probably street hunt till I gain a level then go back to the missions, at least till I get some SO's 
WSs can be hard work at low levels.
I really should do something about this signature.
To be honest I spent most of my time with my WS asploding outdoor mobs and ignoring the missions. They aren't much fun for a soloing lowbie WS. Anyway post-level 12 its more fun to Mire & Blast nicely grouped mobs outdoors I find.
I have had issues with other characters getting things like pairs of +1 lieuts on Heroic though, a Corrupter I play had basically the same problems.
Am I just being unlucky with my new WS or has the way missions are created by the game engine been changed? Every mission (and I mean every single mission) I have tried to solo has been full of +1 mobs. On the lowest setting (heroic) before SO's this is a major pain in the neck considering that in every map there's two or three void stalkers - also +1. I remember we used to have some missions with +1, some even level and the occasional -1 average for the maps as we levelled. This doesn't seem to be happening on this one and it's really starting to get tough.