It depends on the supports and the adcs. For example hard engage supports can, well, hard engage. These are champions like Thresh and Blitzcrank and Nautilus and Alistar for some examples.... if they can engage well on a poke support like Karma, Nami, Zyra, Soraka, Lulu..... then they can normally do quite well. The problem is, poke supports are supposed to poke, not engage. Making life hard for tanky supports, but the damage often times falls off unless its Karma or Zyra.
Tanky supports like Braum are there to soak up damage for the ADC. He and Taric i think are the only two tank supports that just kinda sit back and wait for an opportunity.
It depends on the ADC as well because some ADCs can make life hell for tanky supports. Vayne, Kalista, Lucian, Tristana are some examples. This is however very minor thought process going into it..... simply because this does not take into account the skill levels of each of the players playing the champs, nor taking into account junglers or top lane teles or mid lane roams.