1. 35 guardsman will never be able to hide behind just 2 tanks, especially if they go in anti-blast formation.
2. If you want footslogging guard -- take
DA as allies and put Azrael into 50-men combined squad for fearless and 4++ or your people will be a dead meat.
3. Hellhound is rearly worth it points, it's better to take another Vendetta.
4. If you use psykers -- take full 9 of them, their power depends of their numbers.
5. Consider
HB sponsons for Vendettas -- they are cheap but can be very handy.
6. For plasma-guns it is better to use vets, they are BS4 and waste 1/3-rd less shots then regular guardsmen.
7. For the tanks and other Heavy Support the rule of thumb in "take it in pairs". It is not mandatory but usually useful

.