I also thought the same.
I did Judo with only 6 months of Aikido behind me. I've now been doing Aikido for nearly 2 whole years (wow) and I believe Aikido to work without Judo as long as you work hard at your Aikido.
Judo, no doubt is great. But I felt that for every 2 steps I made forward with AIkido I would take one back with the total attitude and technique difference of Judo.
I have a tremendous amount of respect for Judoka and what they do, as they do it bloody well.
The key factor with Aikido training (in my very humble soon to be blue belt, (hopefully), opinion) is that Aikido NEEDS energy, you need to have Uke being honest, clear, powerful, fast and centered. If you have that then you're on your way.... I think.